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Submitted To:- Submitted By :- Ramandeep Singh Gurvinder Singh Ashish Kapoor Amritpal Singh Jugvinder Singh Sidhu

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this is about scada system how it works and layout


Page 1: Scada & hmi

Submitted To:- Submitted By :-

Ramandeep Singh Gurvinder Singh

Ashish Kapoor

Amritpal Singh

Jugvinder Singh Sidhu

Page 2: Scada & hmi


1. What is SCADA?

2. What is Telemetry?

3. What is Data Acquisition?

4. Differences between SCADA and DCS?

5. Components of SCADA

i. Field Instrumentation

ii. Remote Station

iii. Communication Network

iv. Central Monitoring System


6. Typical System Configuration

7. Modes of Communication

8. SCADA Example Application

9. SCADA System Benefits

10.Futuristic Technoogy for Scada- BAN

11. Limitations


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12. Human Machine Interface(HMI)

i. Introduction ii. Terminology

iii. Defination iv. Goals

13. Human–Machine Interaction

14. Human Machine Interface

15. Design Methodologies

16. Thirteen Principles of Display Design

17. Modalities And Modes

18. Interaction Technique

19. Human Interface Device

20. Biblography

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Supervisory Control And Data Acquisition

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What is SCADA?

SCADA (Supervisory Control And Data Acquisition) system refers to the

combination of telemetry and data acquisition. It consists of collecting

information, transferring it back to a central site, carrying out necessary analysis

and control, and then displaying this data on a number of operator screens.The

SCADA system is used to monitor and control a plant or equipment. Control may

be automatic or can be initiated by operator commands. SCADA systems were first

used in the 1960s

SCADA stands for supervisory control and data acquisition. It generally refers to an industrial control system: a computer system monitoring and controlling a process. The process can be industrial, infrastructure or facility-based as described below:

Industrial processes include those of manufacturing, production, power generation, fabrication, and refining, and may run in continuous, batch, repetitive, or discrete modes.

Infrastructure processes may be public or private, and include water treatment and distribution, wastewater collection and treatment, oil and gas pipelines, electrical power transmission and distribution, Wind Farms, civil defense siren systems, and large communication systems.

Facility processes occur both in public facilities and private ones, including buildings, airports, ships, and space stations. They monitor and control HVAC, access, and energy consumption.

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SCADA Software

The supervisory computer consists of a PC running either Campbell Scientific's HMI software or another vendor's software. InTouch, Intellution, Lookout, and other software packages can be used in conjunction with our OPC client/server software application. Like other HMI software packages, our software provides a graphical interface that the operator uses to view the status of remote sites, acknowledge alarms, and control the units.

What is Telemetry?

Telemetry is usually associated with SCADA systems. It is a technique used in

transmitting and receiving information or data over a medium. The information can

be measurements, such as voltage, speed or flow. These data are transmitted to

another location through a medium such as cable, telephone or radio. Information

may come from multiple locations. A way of addressing these different sites is

incorporated in the system

What is Data Acquisition?

Data acquisition refers to the method used to access and control information or data

from the equipment being controlled and monitored. The data accessed are then

forwarded onto a telemetry system ready for transfer to the different sites. They can

be analog and digital information gathered by sensors, such as flowmeter, ammeter,

etc. It can also be data to control equipment such as actuators, relays, valves, motors,


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What are the differences between


Similar to the SCADA systems are the Distributed Control Systems (DCS). The DCS is

usually used in factories and located within a more confined area. It uses a high-speed

communications medium, such as local area network (LAN). A significant amount of

closed loop control is present on the systemThe SCADA system covers

larger.geographical areas. It may rely on a variety of communication links such as

radio and telephone. Closed loop control is not a high priority in this system.

Supervision vs control

There is, in several industries, considerable confusion over the differences between SCADA systems and distributed control systems (DCS). Generally speaking, a SCADA system usually refers to a system that coordinates, but does not control processes in real time. The discussion on real-time control is muddied somewhat by newer telecommunications technology, enabling reliable, low latency, high speed communications over wide areas. Most differences between SCADA and DCS are culturally determined and can usually be ignored. As communication infrastructures with higher capacity become available, the difference between SCADA and DCS will fade.

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Common system components

A SCADA's System usually consists of the following subsystems:

A Human-Machine Interface or HMI is the apparatus which presents process data to a human operator, and through this, the human operator monitors and controls the process.

A supervisory (computer) system, gathering (acquiring) data on the process and sending commands (control) to the process.

Remote Terminal Units (RTUs) connecting to sensors in the process, converting sensor signals to digital data and sending digital data to the supervisory system.

Programmable Logic Controller (PLCs) used as field devices because they are more economical, versatile, flexible, and configurable than special-purpose RTUs.

Communication infrastructure connecting the supervisory system to the Remote Terminal Units

Systems concepts

The term SCADA usually refers to centralized systems which monitor and control entire sites, or complexes of systems spread out over large areas (anything between an industrial plant and a country). Most control actions are performed automatically by Remote Terminal Units ("RTUs") or by programmable logic controllers ("PLCs"). Host control functions are usually restricted to basic overriding or supervisory level intervention. For example, a PLC may control the flow of cooling water through part of an industrial process, but the SCADA system may allow operators to change the set points for the flow, and enable alarm conditions, such as loss of flow and high temperature, to be displayed and recorded. The feedback control loop passes through the RTU or PLC, while the SCADA system monitors the overall performance of the loop.

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Data acquisition begins at the RTU or PLC level and includes meter readings and equipment status reports that are communicated to SCADA as required. Data is then compiled and formatted in such a way that a control room operator using the HMI can make supervisory decisions to adjust or override normal RTU (PLC) controls. Data may also be fed to a Historian, often built on a commodity Database Management System, to allow trending and other analytical auditing.

SCADA systems typically implement a distributed database, commonly referred to as a tag database, which contains data elements called tags or points. A point represents a single input or output value monitored or controlled by the system. Points can be either "hard" or "soft". A hard point represents an actual input or output within the system, while a soft point results from logic and math operations applied to other points. (Most implementations conceptually remove the distinction by making every property a "soft" point expression, which may, in the simplest case, equal a single hard point.) Points are normally stored as value-timestamp pairs: a value, and the timestamp when it was recorded or calculated. A series of value-timestamp pairs gives the history of that point. It's also common to store additional metadata with tags, such as the path to a field device or PLC register, design time comments, and alarm information.

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Human Machine Interface

Typical Basic SCADA Animations

A Human-Machine Interface or HMI is the apparatus which presents process data to a human operator, and through which the human operator controls the process.

An HMI is usually linked to the SCADA system's databases and software programs, to provide trending, diagnostic data, and management information such as scheduled maintenance procedures, logistic information, detailed schematics for a particular sensor or machine, and expert-system troubleshooting guides.

The HMI system usually presents the information to the operating personnel graphically, in the form of a mimic diagram. This means that the operator can see a schematic representation of the plant being controlled. For example, a picture of a pump connected to a pipe can show the operator that the pump is running and how much fluid it is pumping through the pipe at the moment. The operator can then switch the pump off. The HMI software will show the flow rate of the fluid in the pipe decrease in real time. Mimic diagrams may consist of line graphics and schematic symbols to represent process elements, or may consist of digital photographs of the process equipment overlain with animated symbols.

The HMI package for the SCADA system typically includes a drawing program that the operators or system maintenance personnel use to change the way these points are represented in the interface. These representations can be as simple as an on-screen traffic light, which represents the state of an actual traffic light in

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the field, or as complex as a multi-projector display representing the position of all of the elevators in a skyscraper or all of the trains on a railway.

An important part of most SCADA implementations is alarm handling. The system monitors whether certain alarm conditions are satisfied, to determine when an alarm event has occurred. Once an alarm event has been detected, one or more actions are taken (such as the activation of one or more alarm indicators, and perhaps the generation of email or text messages so that management or remote SCADA operators are informed). In many cases, a SCADA operator may have to acknowledge the alarm event; this may deactivate some alarm indicators, whereas other indicators remain active until the alarm conditions are cleared. Alarm conditions can be explicit - for example, an alarm point is a digital status point that has either the value NORMAL or ALARM that is calculated by a formula based on the values in other analogue and digital points - or implicit: the SCADA system might automatically monitor whether the value in an analogue point lies outside high and low limit values associated with that point. Examples of alarm indicators include a siren, a pop-up box on a screen, or a coloured or flashing area on a screen (that might act in a similar way to the "fuel tank empty" light in a car); in each case, the role of the alarm indicator is to draw the operator's attention to the part of the system 'in alarm' so that appropriate action can be taken. In designing SCADA systems, care is needed in coping with a cascade of alarm events occurring in a short time, otherwise the underlying cause (which might not be the earliest event detected) may get lost in the noise. Unfortunately, when used as a noun, the word 'alarm' is used rather loosely in the industry; thus, depending on context it might mean an alarm point, an alarm indicator, or an alarm event.

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Components of SCADA System

Components of a SCADA System A SCADA system are composed of the following:

1. Field Instrumentation

2. Remote Stations

3. Communications Network

4. Central Monitoring Station

Field Instrumentation refers to the sensors and actuators that are directly interfaced

to the plant or equipment. They generate the analog and digital signals that will be

monitored by the Remote Station. Signals are also conditioned to make sure they are

compatible with the inputs/outputs of the RTU or PLC at the Remote Station.

The Remote Station is installed at the remote plant or equipment being monitored

and controlled by the central host computer. This can be a Remote Terminal Unit

(RTU) or a Programmable Logic Controller (PLC).

The Communications Network is the medium for transferring information from one

location to another. This can be via telephone line, radio or cable.

The Central Monitoring Station (CMS) refers to the location of the master or host

computer. Several workstation may be configured on the CMS, if necessary. It uses a

Man Machine

Interface (MMI) program to monitor various types data needed for the operation. The

following is a sample configuration of a SCADA system for water distribution.

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SCADA Component:

Field Instrumentation

Field Instrumentation refers to the devices that are connected to the equipment or

machines being controlled and monitored by the SCADA system. These are sensors

for monitoring certain parameters; and actuators for controlling certain modules of

the system.

These instruments convert physical parameters (i.e., fluid flow, velocity, fluid level,

etc.) to electrical signals (i.e.voltage or current) readable by the Remote Station

equipment. Outputs can either be in analog (continuous range) or in digital (discrete

values). Some of the industry standard analog outputs of these sensors are 0 to 5

volts, 0 to 10 volts, 4 to 20 mA and 0 to 20 mA. The voltage outputs are used when

the sensors are installed near the controllers (RTU or PLC). The current outputs are

used when the sensors are located far from the controllers.

Digital outputs are used to differentiate the discrete status of the equipment. Usually,

<1> is used to mean EQUIPMENT ON and <0> for EQUIPMENT OFF status. This may

also mean <1> for FULL or <0> for EMPTY.

Actuators are used to turn on or turn off certain equipment. Likewise, digital and

analog inputs are used for control. For example, digital inputs can be used to turn on

and off modules on equipment. While analog inputs are used to control the speed of

a motor or the position of a motorized valve.

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Remote Station

Field instrumentation connected to the plant or equipment being monitored and

controlled are interfaced to the Remote Station to allow process manipulation at a

remote site. It is also used to gather data from the equipment and transfer them to

the central SCADA system. The Remote Station may either be an RTU (Remote

Terminal Unit) or a PLC (Programmable Logic Controller). It may also be a single board

or modular unit.

RTU versus PLC

The RTU (Remote Terminal Unit) is a ruggedized computer with very good radio

interfacing. It is used in situations where communications are more difficult. One

disadvantage of the RTU is its poor programmability. However, modern RTUs are now

offering good programmability comparable to PLCs.

The PLC (Programmable Logic Controller) is a small industrial computer usually found

in factories. Its main use is to replace the relay logic of a plant or process. Today,

the PLC is being used in SCADA systems to due its very good programmability. Earlier

PLC’s have no serial communication ports for interfacing to radio for transferring

of data. Nowadays, PLC's have extensive communication features and a wide support

for popular radio units being used for SCADA system. In the near future we are seeing

the merging of the RTUs and the PLC’s.

Micrologic is offering an inexpensive RTU for SCADA system wherein the PLC may be

an overkill solution. It is a microcontroller-based RTU and can be interfaced to radio

modems for transmitting of data to the CMS.

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Single Board versus Modular Unit

The Remote Station is usually available in two types, namely, the single board and the

modular unit. The single board provides a fixed number of input/output (I/O)

interfaces. It is cheaper, but does not offer easy expandability to a more sophisticated

system. The modular type is an expandable remote station and more expensive than

the single board unit. Usually a back plane is used to connect the modules. Any I/O or

communication modules needed for future expansion may be easily plugged in on the


Communication Network

The Communication Network refers to the communication equipment needed to

transfer data to and from different sites. The medium used can either be cable,

telephone or radio. The use of cable is usually implemented in a factory. This is not

practical for systems covering large geographical areas because of the high cost of the

cables, conduits and the extensive labor in installing them.The use of telephone lines

(i.e., leased or dial-up) is a cheaper solution for systems with large coverage. The

leased line is used for systems requiring on-line connection with the remote stations.

This is expensive since one telephone line will be needed per site. Besides leased lines

are more expensive than ordinary telephone line. Dial-up lines can be used on

systems requiring updates at regular intervals (e.g., hourly updates). Here ordinary

telephone lines can be used. The host can dial a particular number of a remote site to

get the readings and send commands. Remote sites are usually not accessible by

telephone lines. The use of radio offers an economical solution. Radio modems are

used to connect the remote sites to the host. An on-line operation can also be

implemented on the radio system. For locations wherein a direct radio link cannot be

established, a radio repeater is used to link these sites.

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Central Monitoring Station (CMS)

The Central Monitoring Station (CMS) is the master unit of the SCADA system. It is in

charge of collecting information gathered by the remote stations and of generating

necessary action for any event detected. The CMS can have a single computer

configuration or it can be networked to workstations to allow sharing of information

from the SCADA system.

A Man-Machine Interface (MMI) program will be running on the CMS computer. A

mimic diagram of the whole plant or process can be displayed onscreen for easier

identification with the real system. Each I/O point of the remote units can be

displayed with corresponding graphical representation and the present I/O reading.

The flow reading can be displayed on a graphical representation of a flowmeter. A

reservoir can be displayed with the corresponding fluid contents depending on the

actual tank level. Set-up parameters such as trip values, limits, etc. are entered on

this program and downloaded to the corresponding remote units for updating of their

operating parameters.

The MMI program can also create a separate window for alarms. The alarm window

can display the alarm tag name, description, value, trip point value, time, date and

other pertinent information. All alarms will be saved on a separate file for later

review. A trending of required points can be programmed on the system. Trending

graphs can be viewed or printed at a later time. Generation of management reports

can also be scheduled on for a specific time of day, on a periodic basis, upon operator

request, or event initiated alarms. Access to the program is permitted only to

qualified operators. Each user is given a password and a privilege level to access only

particular areas of the program.. All actions taken by the users are logged on a file for

later review.

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MMI Screen Showing Pipe System Diagram and Repair Areas

Typical System Configurations

There are two typical network configurations for the wireless telemetry radio-based

SCADA systems. They are the point-to-point and the point-to-multipoint


1.Point-to-Point Configuration

2.Point-to-Multipoint Configuration

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1.Point-to-Point Configuration

The Point-to-Point configuration is the simplest set-up for a telemetry system. Here

data is exchanged between two stations. One station can be set up as the master and

the other as the slave. An example is a set-up of two RTUs: one for a reservoir or tank

and the other for a water pump at a different location. Whenever the tank is nearly

empty, the RTU at the tank will send an EMPTY command to the other RTU. Upon

receiving this command, the RTU at the water pump will start pumping water to the

tank. When the tank is full, the tank’s RTU will send a FULL command to the pump’s

RTU to stop the motor.

Point-to-Point Configuration

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2.Point-to-Multipoint Configuration

The Point-to-Multipoint configuration is where one device is designated as the master

unit to several slave units. The master is usually the main host and is located at the

control room. While the slaves are the remote units at the remote sites. Each slave is

assigned a unique address or identification number.

Point-to-Multipoint Configuration

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Modes of Communication

There are two modes of communication available, namely, the polled system and the

interrupt system.

1.Polled System

In the Polled or Master/Slave system, the master is in total control of

communications. The master makes a regular polling of data (i.e., sends and receives

data) to each slave in sequence. The slave unit responds to the master only when it

receivers a request. This is called the half-duplex method. Each slave unit will have its

own unique address to allow correct identification. If a slave does not respond for a

predetermined period of time, the master retries to poll it for a number of times

before continuing to poll the next slave unit.


• Process of data gathering is fairly simple

• No collision can occur on the network

• Link failure can easily be detected


• Interrupt type request from a slave requesting immediate action cannot be handled


• Waiting time increases with the number of slaves

• All communication between slaves have to pass through the master with added


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2.Interrupt System

The interrupt system is also referred to as Report by Exception (RBE) configured

system. Here the slave monitors its inputs. When it detects a significant change or

when it exceeds a limit, the slave initiates communication to the master and transfers

data. The system is designed with error detection and recovery process to cope with

collisions. Before any unit transmits, it must first check if any other unit is

transmitting. This can be done by first detecting the carrier of the transmission

medium. If another unit is transmitting, some form of random delay time is required

before it tries again. Excessive collisions result to erratic system operation and

possible system failure. To cope with this, if after several attempts, the slave still fails

to transmit a message to the master, it waits until polled by the master.


• System reduces unnecessary transfer of data as in polled systems

• Quick detection of urgent status information

• Allows slave-to-slave communication


• Master may only detect a link failure after a period of time, that is, when system is


• Operator action is needed to have the latest values

Collision of data may occur and may cause delay in the communication

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SCADA Example Application

Sedimentation Tank

Monitor on/off status of pumps Control coliform, TSS, and on/off status of pumps


Monitor torque Control on/off status and torque alarms


Monitor and control temperatures and flow rates within exhaust heat recovery unit and heat exchanger

Trickling Filter Monitor on/off status of pumps and blowers, dissolved oxygen, flow rate, and wetwell level Control on/off status of pumps and blowers

Chlorine Contact Tank

Monitor ORP Control Cl2and SO2 injection


Monitor and control temperature

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SCADA System Benefits

1. Control units function as PLCs, RTUs, or DCUs. 2. Control units perform advanced measurement and control independent of

the central computer. 3. PID control continues, even if communications to the main computer are

lost. 4. Control units have many channel types to measure most available sensors. 5. Systems are compatible with our own or other vendors' HMI software

packages. 6. Control units have their own UPS; during ac power loss, they continue to

measure and store time-stamped data. 7. Control units provide on-board statistical and mathematical processing. 8. Systems are easily expandable: add new sites or add sensors to existing

sites. 9. Control units have wide operating temperature ranges and operate in

rugged environments.

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Futuristic Technoogy for Scada- BAN

What is BAN ?

BAN –Body Area Network

Still under research at Chiba University Japan under supervision of Prof. Hideyuki Nebiya

This technology works on the basic principle that human body poses its own Electric Field and is a good conductor of electricity.

Prof. Nebiya and his team found that human body posses an electric field of its own and when ever human body comes in contact with some electrical equipment say if someone touch TV Screen ; the intensity of body electric field increases considerably.

From the above research, they concluded that human body can be used for transmission using different frequency signals.

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What human body communication is?

It is a means of communication between devices via the human body. It will contribute to a reduction in information leakage because the communication is carried out via the human body. In addition, the transmission loss is believed to be smaller compared with that of wireless spatial transmission, realizing wireless communication with low power consumption.

In this technology an electronic card is used which acts as transmitter. Signals are transmitted through human body. Receiver on the other side receives the signal and respond back that signal has received and acts accordingly.

Electronic Receiver Electronic Transmitter

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APPLICATIONS It can be used for locking and unlocking of doors as well as medical and health care purposes. It can also be adopted by the entertainment field for transmission of music and image information. And don't forget automotive keyless entry systems and wearable computing systems.


In Medical Field, a wrist watch like equipment is give to patient to wear which keeps an eye on the state of patient and records every second change that take place in patient’s body. Nurses also wear similar device , when they touch the patient the whole dat gets transferred to the nurse’s device which is then transmitted to the concernd Doctor. In this way many patients can be monitored at a same time from a central control room using SCADA.

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In this field this technology plays a vital role, the company officials need not to carry bulky files or even a pen to sign the contract , all data is stored in there Electronic Data Cards which is transferred to other person on permission. To sign the contract 2 persons just need to shake hand and there signed contracts exchanged through there Electronic Data Cards

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3. Entertainment Industry

In this field this technology is going to flourish at maximum rate. Just with the simple example you can get an idea how useful and amazing development its going to make in this sector.

Now a days Ipod have wires for the head phones but with this technology there is no need for wired head phones. Just switch on the music player and put on your headphones and enjoy. Human both acts as carrier in this case.

This is not over yet real application is now to start ,imagine your friend also want to listen the same music what he has to do is to wear a headset and just hold your hand and its done. In similar way upto 15 persons can get connect and listen music at same time. Further research is needed to develop it further to higher levels.

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How about the progress in the development of its usage and market?

A number of companies have been working on the employment of human body communication technologies and actually developed prototypes. A variety of companies, including electronic manufacturers, mobile phone companies, office equipment manufacturers, automobile manufacturers and house builders, showed demonstrations. In the demonstrations, they used the products incorporating human body communication technologies, such as keys for locking and unlocking, cash registers for retail shops and transmission and common use of video, music and textual information in the entertainment field. Some demonstrations could be seen at Security Show 2009 and IC Card World 2009, both of which took place in March 2009 We have recently received many inquiries about their applications to sensor networks, which are drawing attention from not only the industrial sector but also from the medical and healthcare sectors. People in medical organizations and healthcare companies seem to be placing greater expectations on human body communication technologies probably because the human body information gained by sensing can be transmitted to devices via the human body.



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Like every other technology, this technology also have some limitations

some are as follows :-

1. Loss of information and threat of stealing important information.

2. Physical effects on human body.

Researchers are still working on these factors to use it


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To work with a system, users have to be able to control and assess the state of the system. For example, when driving an automobile, the driver uses the steering wheel to control the direction of the vehicle, and the accelerator pedal, brake pedal and gearstick to control the speed of the vehicle. The driver perceives the position of the vehicle by looking through the windshield and exact speed of the vehicle by reading the speedometer. The user interface of the automobile is on the whole composed of the instruments the driver can use to accomplish the tasks of driving and maintaining the automobile.


There is a distinct difference between User Interface versus Operator Interface or Human Machine Interface (HMI).

The term user interface is often used in the context of (personal) computer systems and electronic devices

o where a network of equipment or computers are interlinked through an MES (Manufacturing Execution System)-or Host.

o An HMI is typically local to one machine or piece of equipment, and is the interface method between the human and the equipment/machine. An Operator interface is the interface method by which multiple equipment that are linked by a host control system is accessed or controlled.

The system may expose several user interfaces to serve different kinds of users. For example, a computerized library database might provide two user interfaces, one for library patrons (limited set of functions, optimized for ease of use) and the other for library personnel (wide set of functions, optimized for efficiency).The user interface of a mechanical system, a vehicle or an industrial installation is sometimes referred to as the human-

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machine interface (HMI). HMI is a modification of the original term MMI (man-machine interface). In practice, the abbreviation MMI is still frequently used although some may claim that MMI stands for something different now. Another abbreviation is HCI, but is more commonly used for than human-computer interface. Other terms used are operator interface console (OIC) and operator interface terminal (OIT). However it is abbreviated, the terms refer to the 'layer' that separates a human that is operating a machine from the machine itself.

In science fiction, HMI is sometimes used to refer to what is better described as direct neural interface. However, this latter usage is seeing increasing application in the real-life use of (medical) prostheses—the artificial extension that replaces a missing body part (e.g., cochlear implants).

In some circumstance computers might observe the user, and react according to their actions without specific commands. A means of tracking parts of the body is required, and sensors noting the position of the head, direction of gaze and so on have been used experimentally. This is particularly relevant to immersive interfaces.

Definition: The Human-Machine Interface is quite literally where the human

and the machine meet. It is the area of the human and the area of the machine that interact during a given task.

Interaction can include touch, sight, sound, heat transference or any other physical or cognitive function.

Also Known As: Man-Machine Interface Examples: A typical computer station will have four human-machine interfaces, the keyboard (hand), the mouse (hand), the monitor (eyes) and the speakers (ears).

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A basic goal of HMI is to improve the interactions between users and machines(computers) by making computers more usable and receptive to the user's needs. Specifically, HMI is concerned with:

methodologies and processes for designing interfaces (i.e., given a task and a class of users, design the best possible interface within given constraints, optimizing for a desired property such as learning ability or efficiency of use)

methods for implementing interfaces (e.g. software toolkits and libraries; efficient algorithms)

techniques for evaluating and comparing interfaces developing new interfaces and interaction techniques developing descriptive and predictive models and theories of interaction

A long term goal of HMI is to design systems that minimize the barrier between the human's cognitive model of what they want to accomplish and the computer's understanding of the user's task.

Professional practitioners in HMI are usually designers concerned with the practical application of design methodologies to real-world problems. Their work often revolves around designing graphical user interfaces and web interfaces.

Researchers in HMI are interested in developing new design methodologies, experimenting with new hardware devices, prototyping new software systems, exploring new paradigms for interaction, and developing models and theories of interaction.

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Human–Machine interaction (HMI) is the study of interaction between people (users) and Machines(Computers). Interaction between users and machines occurs at the user interface (or simply interface), which includes both software and hardware; for example, characters or objects displayed by software on a personal computer's monitor, input received from users via hardware peripherals such as keyboards and mice, and other user interactions with large-scale computerized systems such as aircraft and power plants. The Association for Computing Machinery defines human-machine interaction as "a discipline concerned with the design, evaluation and implementation of interactive computing systems for human use and with the study of major phenomena surrounding them”. An important fact of HMI is the securing of user satisfaction

Because human-machine interaction studies a human and a machine in conjunction, it draws from supporting knowledge on both the machine and the human side. On the machine side, techniques in computer graphics, operating systems, programming languages, and development environments are relevant. On the human side, communication theory, graphic and industrial design disciplines, linguistics, social sciences, cognitive psychology, and human factors are relevant. Engineering and design methods are also relevant. Due to the multidisciplinary nature of HCI, people with different backgrounds contribute to its success. HCI is also sometimes referred to as human–machine interaction (HMI) or computer–human interaction (CHI).

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The Human–Machine (computer) interface can be described as the point of communication between the human user and the computer. The flow of information between the human and computer is defined as the loop of interaction. The loop of interaction has several aspects to it including:

Task Environment: The conditions and goals set upon the user. Machine Environment: The environment that the computer is connected

to, i.e. a laptop in a college student's dorm room. Areas of the Interface: Non-overlapping areas involve processes of the

human and computer not pertaining to their interaction. Meanwhile, the overlapping areas only concern themselves with the processes pertaining to their interaction.

Input Flow: The flow of information that begins in the task environment, when the user has some task that requires using their computer.

Output: The flow of information that originates in the machine environment.

Feedback: Loops through the interface that evaluate, moderate, and confirm processes as they pass from the human through the interface to the computer and back.

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User interfaces are considered by some authors to be a prime ingredient of Computer user satisfaction.

The design of a user interface affects the amount of effort the user must expend to provide input for the system and to interpret the output of the system, and how much effort it takes to learn how to do this. Usability is the degree to which the design of a particular user interface takes into account the human psychology and physiology of the users, and makes the process of using the system effective, efficient and satisfying

Usability is mainly a characteristic of the user interface, but is also associated with the functionalities of the product and the process to design it. It describes how well a product can be used for its intended purpose by its target users with efficiency, effectiveness, and satisfaction, also taking into account the requirements from its context of use.


A key property of a good user interface is consistency. There are three important aspects.First, the controls for different features should be presented in a consistent manner so that users can find the controls easily.For example, users find it very difficult to use software when some commands are available through menus, some through icons, and some through right-clicks. A good user interface might provide shortcuts or "synonyms" that provide parallel access to a feature, but users do not have to search multiple sources to find what they're looking for.Second, the "principle of least astonishment" is crucial. Various features should work in similar ways. For example, some features in Adobe Acrobat are "select tool, then select text to which apply." Others are "select text, then apply action to selection."

Third, user interfaces should not change version-to-version—user interfaces must remain upward compatible.

Good user interface design is about setting and meeting user expectations.Better (from a programmer's point of view) is not better. The same (from a user's point of view) is better.

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In computer science and human-computer interaction, the user interface (of a computer program) refers to the graphical, textual and auditory information the program presents to the user, and the control sequences (such as keystrokes with the computer keyboard, movements of the computer mouse, and selections with the touchscreen) the user employs to control the program.


Currently (as of 2009) the following types of user interface are the most common:

Graphical user interfaces (GUI) accept input via devices such as computer keyboard and mouse and provide articulated graphical output on the computer monitor. There are at least two different principles widely used in GUI design: Object-oriented user interfaces (OOUIs) and application oriented interfaces[verification needed].

Web-based user interfaces or web user interfaces (WUI) accept input and provide output by generating web pages which are transmitted via the Internet and viewed by the user using a web browser program. Newer implementations utilize Java, AJAX, Adobe Flex, Microsoft .NET, or similar technologies to provide real-time control in a separate program, eliminating the need to refresh a traditional HTML based web browser. Administrative web interfaces for web-servers, servers and networked computers are often called Control panels.

User interfaces that are common in various fields outside desktop computing:

Command line interfaces, where the user provides the input by typing a command string with the computer keyboard and the system provides output by printing text on the computer monitor. Used by programmers and system administrators, in engineering and scientific environments, and by technically advanced personal computer users.

Tactile interfaces supplement or replace other forms of output with haptic feedback methods. Used in computerized simulators etc.

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Touch user interface are graphical user interfaces using a touchscreen display as a combined input and output device. Used in many types of point of sale, industrial processes and machines, self-service machines etc.

Other types of user interfaces:

Attentive user interfaces manage the user attention deciding when to interrupt the user, the kind of warnings, and the level of detail of the messages presented to the user.

Batch interfaces are non-interactive user interfaces, where the user specifies all the details of the batch job in advance to batch processing, and receives the output when all the processing is done. The computer does not prompt for further input after the processing has started.

Conversational Interface Agents attempt to personify the computer interface in the form of an animated person, robot, or other character (such as Microsoft's Clippy the paperclip), and present interactions in a conversational form.

Crossing-based interfaces are graphical user interfaces in which the primary task consists in crossing boundaries instead of pointing.

Gesture interface are graphical user interfaces which accept input in a form of hand gestures, or mouse gestures sketched with a computer mouse or a stylus.

Intelligent user interfaces are human-machine interfaces that aim to improve the efficiency, effectiveness, and naturalness of human-machine interaction by representing, reasoning, and acting on models of the user, domain, task, discourse, and media (e.g., graphics, natural language, gesture).

Motion tracking interfaces monitor the user's body motions and translate them into commands, currently being developed by Apple[2]

Multi-screen interfaces, employ multiple displays to provide a more flexible interaction. This is often employed in computer game interaction in both the commercial arcades and more recently the handheld markets.

Noncommand user interfaces, which observe the user to infer his / her needs and intentions, without requiring that he / she formulate explicit commands.

Object-oriented user interface (OOUI)

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Reflexive user interfaces where the users control and redefine the entire system via the user interface alone, for instance to change its command verbs. Typically this is only possible with very rich graphic user interfaces.

Tangible user interfaces, which place a greater emphasis on touch and physical environment or its element.

Task-Focused Interfaces are user interfaces which address the information overload problem of the desktop metaphor by making tasks, not files, the primary unit of interaction

Text user interfaces are user interfaces which output text, but accept other form of input in addition to or in place of typed command strings.

Voice user interfaces, which accept input and provide output by generating voice prompts. The user input is made by pressing keys or buttons, or responding verbally to the interface.

Natural-Language interfaces - Used for search engines and on webpages. User types in a question and waits for a response.

Zero-Input interfaces get inputs from a set of sensors instead of querying the user with input dialogs.

Zooming user interfaces are graphical user interfaces in which information objects are represented at different levels of scale and detail, and where the user can change the scale of the viewed area in order to show more detail.

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When evaluating a current user interface, or designing a new user interface, it is important to keep in mind the following experimental design principles:

Early focus on user(s) and task(s): Establish how many users are needed to perform the task(s) and determine who the appropriate users should be; someone that has never used the interface, and will not use the interface in the future, is most likely not a valid user. In addition, define the task(s) the users will be performing and how often the task(s) need to be performed.

Empirical measurement: Test the interface early on with real users who come in contact with the interface on an everyday basis. Keep in mind that results may be altered if the performance level of the user is not an accurate depiction of the real human-computer interaction. Establish quantitative usability specifics such as: the number of users performing the task(s), the time to complete the task(s), and the number of errors made during the task(s).

Iterative design: After determining the users, tasks, and empirical measurements to include, perform the following iterative design steps:

1. Design the user interface 2. Test 3. Analyze results 4. Repeat

Repeat the iterative design process until a sensible, user-friendly interface is created.

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A number of diverse methodologies outlining techniques for Human–Machine interaction design have emerged since the rise of the field in the 1980s. Most design methodologies stem from a model for how users, designers, and technical systems interact. Early methodologies, for example, treated users' cognitive processes as predictable and quantifiable and encouraged design practitioners to look to cognitive science results in areas such as memory and attention when designing user interfaces. Modern models tend to focus on a constant feedback and conversation between users, designers, and engineers and push for technical systems to be wrapped around the types of experiences users want to have, rather than wrapping user experience around a completed system.

User-centered design: user-centered design (UCD) is a modern, widely practiced design philosophy rooted in the idea that users must take center-stage in the design of any computer system. Users, designers and technical practitioners work together to articulate the wants, needs and limitations of the user and create a system that addresses these elements. Often, user-centered design projects are informed by ethnographic studies of the environments in which users will be interacting with the system. This practice is similar but not identical to Participatory Design, which emphasizes the possibility for end-users to contribute actively through shared design sessions and workshops.

Principles of User Interface Design: these are seven principles that may be considered at any time during the design of a user interface in any order, namely Tolerance, Simplicity, Visibility, Affordance, Consistency, Structure and Feedback.

Display designs :-Displays are human-made artifacts designed to support the perception of relevant system variables and to facilitate further processing of that information. Before a display is designed, the task that the display is intended to support must be defined (e.g. navigating, controlling, decision making, learning, entertaining, etc.). A user or operator must be able to process whatever information that a system generates and displays; therefore, the information must be displayed according to principles in a manner that will support perception, situation awareness, and understanding.

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These principles of human perception and information processing can be utilized to create an effective display design. A reduction in errors, a reduction in required training time, an increase in efficiency, and an increase in user satisfaction are a few of the many potential benefits that can be achieved through utilization of these principles.

Certain principles may not be applicable to different displays or situations. Some principles may seem to be conflicting, and there is no simple solution to say that one principle is more important than another. The principles may be tailored to a specific design or situation. Striking a functional balance among the principles is critical for an effective design.

Perceptual Principles

1. Make displays legible (or audible)

A display’s legibility is critical and necessary for designing a usable display. If the characters or objects being displayed cannot be discernible, then the operator cannot effectively make use of them.

2. Avoid absolute judgment limits

Do not ask the user to determine the level of a variable on the basis of a single sensory variable (e.g. color, size, loudness). These sensory variables can contain many possible levels.

3. Top-down processing

Signals are likely perceived and interpreted in accordance with what is expected based on a user’s past experience. If a signal is presented contrary to the user’s expectation, more physical evidence of that signal may need to be presented to assure that it is understood correctly.

4. Redundancy gain

If a signal is presented more than once, it is more likely that it will be understood correctly. This can be done by presenting the signal in alternative physical forms

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(e.g. color and shape, voice and print, etc.), as redundancy does not imply repetition. A traffic light is a good example of redundancy, as color and position are redundant.

5. Similarity causes confusion: Use discriminable elements

Signals that appear to be similar will likely be confused. The ratio of similar features to different features causes signals to be similar. For example, A423B9 is more similar to A423B8 than 92 is to 93. Unnecessary similar features should be removed and dissimilar features should be highlighted.

Mental Model Principles

6. Principle of pictorial realism

A display should look like the variable that it represents (e.g. high temperature on a thermometer shown as a higher vertical level). If there are multiple elements, they can be configured in a manner that looks like it would in the represented environment.

7. Principle of the moving part

Moving elements should move in a pattern and direction compatible with the user’s mental model of how it actually moves in the system. For example, the moving element on an altimeter should move upward with increasing altitude.

Principles Based on Attention

8. Minimizing information access cost

When the user’s attention is diverted from one location to another to access necessary information, there is an associated cost in time or effort. A display design should minimize this cost by allowing for frequently accessed sources to be located at the nearest possible position. However, adequate legibility should not be sacrificed to reduce this cost.

9. Proximity compatibility principle

Divided attention between two information sources may be necessary for the completion of one task. These sources must be mentally integrated and are

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defined to have close mental proximity. Information access costs should be low, which can be achieved in many ways (e.g. proximity, linkage by common colors, patterns, shapes, etc.). However, close display proximity can be harmful by causing too much clutter.

10. Principle of multiple resources

A user can more easily process information across different resources. For example, visual and auditory information can be presented simultaneously rather than presenting all visual or all auditory information.

Memory Principles

11. Replace memory with visual information: knowledge in the world

A user should not need to retain important information solely in working memory or to retrieve it from long-term memory. A menu, checklist, or another display can aid the user by easing the use of their memory. However, the use of memory may sometimes benefit the user by eliminating the need to reference some type of knowledge in the world (e.g. an expert computer operator would rather use direct commands from memory than refer to a manual). The use of knowledge in a user’s head and knowledge in the world must be balanced for an effective design.

12. Principle of predictive aiding

Proactive actions are usually more effective than reactive actions. A display should attempt to eliminate resource-demanding cognitive tasks and replace them with simpler perceptual tasks to reduce the use of the user’s mental resources. This will allow the user to not only focus on current conditions, but also think about possible future conditions. An example of a predictive aid is a road sign displaying the distance from a certain destination

13. Principle of consistency

Old habits from other displays will easily transfer to support processing of new displays if they are designed in a consistent manner. A user’s long-term memory will trigger actions that are expected to be appropriate. A design must accept this fact and utilize consistency among different displays.

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A modality is a path of communication employed by the user interface to carry input and output. Examples of modalities:

Input — computer keyboard allows the user to enter typed text, digitizing tablet allows the user to create free-form drawing

Output — computer monitor allows the system to display text and graphics (vision modality), loudspeaker allows the system to produce sound (auditory modality)

The user interface may employ several redundant input modalities and output modalities, allowing the user to choose which ones to use for interaction.

A mode is a distinct method of operation within a computer program, in which the same input can produce different perceived results depending of the state of the computer program. Heavy use of modes often reduces the usability of a user interface, as the user must expend effort to remember current mode states, and switch between mode states as necessary

In the industrial design field of human-machine interaction, the user interface is (a place) where interaction between humans and machines occurs. The goal of interaction between a human and a machine at the user interface is effective operation and control of the machine, and feedback from the machine which aids the operator in making operational decisions. Examples of this broad concept of user interfaces include the interactive aspects of computer operating systems, hand tools, heavy machinery operator controls. and process controls. The design considerations applicable when creating user interfaces are related to or involve such disciplines as ergonomics and psychology.

A user interface is the system by which people (users) interact with a machine. The user interface includes hardware (physical) and software (logical) components. User interfaces exist for various systems, and provide a means of:

Input, allowing the users to manipulate a system, and/or Output, allowing the system to indicate the effects of the users'


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Generally, the goal of human-machine interaction engineering is to produce a user interface which makes it easy, efficient, enjoyable to operate a machine in the way which produces the desired result. This generally means that the operator needs to provide minimal input to achieve the desired output, and also that the machine minimizes undesired outputs to the human.

Ever since the increased use of personal computers and the relative decline in societal awareness of heavy machinery, the term user interface has taken on overtones of the (graphical) user interface, while industrial control panel and machinery control design discussions more commonly refer to human-machine interfaces.

Other terms for user interface include human-computer interface (HCI) and man-machine interface (MMI).

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Fold n' Drop, a crossing-based interaction technique for dragging and dropping

files between overlapping windows.

An interaction technique, user interface technique or input technique is a combination of hardware and software elements that provides a way for computer users to accomplish a single task. For example, one can go back to the previously visited page on a Web browser by either clicking a button, pressing a key, performing a mouse gesture or uttering a speech command. It is a key concept in human-computer interaction.


Although there is no general agreement on the exact meaning of the term "interaction technique", the most popular definition is from the computer graphics literature:

An interaction technique is a way of using a physical input/output device to perform a generic task in a human-computer dialogue.

A more recent variation is: An interaction technique is the fusion of input and

output, consisting of all software and hardware elements, that provides a way for

the user to accomplish a task.

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The computing view

From the computer's perspective, an interaction technique involves:

One or several input devices that capture user input, One or several output devices that display user feedback, A piece of software that:

o interprets user input into commands the computer can understand, o produces user feedback based on user input and the system's state.

Consider for example the process of deleting a file using a contextual menu. This assumes the existence of a mouse (input device), a screen (output device), and a piece of code that paints a menu and updates its selection (user feedback) and sends a command to the file system when the user clicks on the "delete" item (interpretation). User feedback can be further used to confirm that the command has been invoked.

The user's view

From the user's perspective, an interaction technique is a way to perform a single computing task and can be informally expressed with user instructions or usage scenarios. For example "to delete a file, right-click on the file you want to delete, then click on the delete item".

The designer's view

From the user interface designer's perspective, an interaction technique is a well-defined solution to a specific user interface design problem. Interaction techniques as conceptual ideas can be refined, extended, modified and combined. For example, contextual menus are a solution to the problem of rapidly selecting commands. Pie menus are a radial variant of contextual menus.

Level of granularity

Interaction techniques are usually fine-grained entities. For example, a desktop environment is too complex to be an interaction technique, whereas Exposé fits the common intuitive understanding of the term perfectly well. In general, a user

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interface can be seen as a combination of many interaction techniques, some of which are not necessarily as explicit as widgets.

Interaction tasks and domain objects

An interaction task is "the unit of an entry of information by the user" [1], such as entering a piece of text, issuing a command, or specifying a 2D position. A similar concept is that of domain object, which is a piece of application data that can be manipulated by the user.[3]

Interaction techniques are the glue between physical I/O devices and interaction tasks or domain objects. Different types of interaction techniques can be used to map a specific device to a specific domain object. For example, different gesture alphabets exist for pen-based text input.

In general, the less compatible the device is with the domain object, the more complex the interaction technique. For example, using a mouse to specify a 2D point involves a trivial interaction technique, whereas using a mouse to rotate a 3D object requires more creativity to design the technique and more lines of code to implement it.

A current trend is to avoid complex interaction techniques by matching physical devices with the task as close as possible, such as exemplified by the field of tangible computing. But this is not always a feasible solution. Furthermore, device/task incompatibilities are unavoidable in computer accessibility, where a single switch can be used to control the whole computer environment.

Interaction style

Interaction techniques that share the same metaphor or design principles can be seen as belonging to the same interaction style. General examples are command line and direct manipulation user interfaces.

Visualization technique

Interaction techniques essentially involve data manipulation and thus place greater emphasis on input than output. Output is merely used to convey affordances and provide user feedback. The use of the term input technique further reinforces the central role of input. Conversely, techniques that mainly

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involve data exploration and thus place greater emphasis on output are called visualization techniques. They are studied in the field of information visualization.

Research and innovation

A large part of research in human-computer interaction involves exploring easier-to-learn or more efficient interaction techniques for common computing tasks. This includes inventing new (post-WIMP) interaction techniques, possibly relying on methods from user interface design, and comparing them with existing techniques using methods from experimental psychology. Examples of scientific venues in these topics are the UIST and the CHI conferences. Other research focuses on the specification of interaction techniques, sometimes using formalisms such as Petri nets for the purposes of formal verification.

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A human interface device or HID is a type of computer device that interacts directly with, and most often takes input from, humans and may deliver output to humans. The term "HID" most commonly refers to the USB-HID specification. The term was coined by Mike Van Flandern of Microsoft when he proposed the USB committee create a Human Input Device class working group.[when?] The working group was renamed as the Human Interface Device class at the suggestion of Tom Schmidt of DEC because the proposed standard supported bi-directional communication.


The primary motivations for HID were to enable innovation in PC input devices and simplify the process of installing these devices. Prior to HID, devices usually conformed to very narrowly defined protocols for mice, keyboards and joysticks (for example the standard mouse protocol at the time supported relative X and Y axis data and binary input for up to two buttons). Any innovation in hardware required overloading the use of data in an existing protocol or creation of custom device drivers and evangelization of a new protocol to application developers. By contrast all HID devices deliver self describing packages that may contain an infinite variety of data types and formats. A single HID driver on the PC parses the data and enables dynamic association of data I/O with application functionality. This has enabled rapid innovation and proliferation of new human interface devices.

The HID standard was developed by a working committee with representatives from several companies and the list of participants can be found in the "Device Class Definition for Human Interface Devices (HID)" document. The concept of a self describing extensible protocol was initially conceived by Mike Van Flandern and Manolito Adan working on a project named Raptor at Microsoft and independently by Steve McGowan working on a device protocol for Access Bus while at Forte. After comparing notes at a Consumer Game Developer Conference, Steve and Mike agreed to collaborate on a new standard for the emerging Universal Serial Bus.

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Hardware input/output devices and peripherals:

List of input devices

o Unit record equipment o Barcode scanner o Keyboard

Computer keyboard Keyboard shortcut Ways to make typing more efficient: command history,

autocomplete, autoreplace and Intellisense o Microphone o Pointing device

Computer mouse Mouse chording

List of output devices

o Visual devices Graphical output device Display device Computer display Video projector Computer printer Plotter

o Auditory devices

Speakers Earphones

o Tactile devices

Refreshable Braille display Braille embosser Haptic devices

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Common HIDs

Keyboard Mouse, Trackball, Touchpad, Pointing

stick Graphics tablet Joystick, Gamepad, Analog stick Webcam Headset

Less common HIDs

Driving simulator devices and flight simulator devices have HIDs such as gear sticks, steering wheels and pedals.

Wired glove (Nintendo Power Glove) Dance pad Wii Remote Surface computing device Apple's Sudden Motion Sensor(SMS)

device in Macs.

Most operating systems will recognize standard USB HID devices, like keyboards and mice, without needing a special driver. When installed, a message saying that a "HID-compliant device" has been recognized generally appears on screen. In comparison, this message does not usually appear for devices connected via the PS/2 6-pin DIN connectors which preceded USB. PS/2 does not support plug-and-play, which means that connecting a PS/2 keyboard or mouse with the computer powered on does not always work. In addition, PS/2 does not support the HID protocol. A USB HID is described by the USB human interface device class.

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Components of the HID protocol

In the HID protocol, there are 2 entities: the "host" and the "device". The device is the entity that directly interacts with a human, such as a keyboard or mouse. The host communicates with the device and receives input data from the device on actions performed by the human. Output data flows from the host to the device and then to the human. The most common example of a host is a computer but some cell phones and PDAs also can be hosts.

The HID protocol makes implementation of devices very simple. Devices define their data packets and then present a "HID descriptor" to the host. The HID descriptor is a hard coded array of bytes that describe the device's data packets. This includes: how many packets the device supports, how large are the packets, and the purpose of each byte and bit in the packet. For example, a keyboard with a calculator program button can tell the host that the button's pressed/released state is stored as the 2nd bit in the 6th byte in data packet number 4 (note: these locations are only illustrative and are device specific). The device typically stores the HID descriptor in ROM and does not need to intrinsically understand or parse the HID descriptor. Some mouse and keyboard hardware in the market today are implemented using only an 8-bit CPU.

The host is expected to be a more complex entity than the device. The host needs to retrieve the HID descriptor from the device and parse it before it can fully communicate with the device. Parsing the HID descriptor can be complicated. Multiple operating systems are known to have shipped bugs in the device drivers responsible for parsing the HID descriptors years after the device drivers were originally released to the public. However, this complexity is the reason why rapid innovation with HID devices is possible.

The above mechanism describes what is known as HID "report protocol". Because it was understood that not all hosts would be capable of parsing HID descriptors, HID also defines "boot protocol". In boot protocol, only specific devices are supported with only specific features because fixed data packet formats are used. The HID descriptor is not used in this mode so innovation is limited. However, the benefit is that minimal functionality is still possible on hosts that otherwise would be unable to support HID. The only devices supported in boot protocol are:-

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Keyboard — Any of the first 256 key codes ("Usages") defined in the HID Usage Tables, Usage Page 7 can be reported by a keyboard using the boot protocol, but most systems only handle a subset of these keys. Most systems support all 104 keys on the IBM AT-101 layout, plus the three new keys designed for Microsoft Windows 95. Many systems also support additional keys on basic western European 105-, Korean 106-, Brazilian ABNT 107- and Japanese DOS/V 109-key layouts. Buttons, knobs and keys that are not reported on Usage Page 7 are not available. For example, a particular US keyboard's QWERTY keys will function but the Calculator and Logoff keys will not because they are defined on Usage Page 12 and cannot be reported in boot protocol.

Mouse — Only the X-axis, Y-axis, and the first 3 buttons will be available. Any additional features on the mouse will not function.

One common usage of boot mode is during the first moments of a computer's boot up sequence. Directly configuring a computer's BIOS is often done using only boot mode.

Other protocols using HID

Since HID's original definition over USB, HID is now also used in other computer communication buses. This enables HID devices that traditionally were only found on USB to also be used on alternative buses. This is done since existing support for USB HID devices can typically be adapted much faster than having to invent an entirely new protocol to support mice, keyboards, and the like. Known buses that use HID are:

Bluetooth HID — Bluetooth is a wireless communications technology. Several Bluetooth mice and keyboards already exist in the market place.

Serial HID — Used in Microsoft's Windows Media Center PC remote control receivers

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