Legacy Voice World

Chapter 03

Analog Connectivity

• What is analog connectivity

• Electric wave forms

• Understanding Analog signaling

Thomas Edison

• Record player• Braille• Home telephone lines• Analog phone lines electricity for voice

transmission

As you speak

• Analog to digital• Properties of electricity as used to convey

properties of voice• Digital to analog

Signaling

• When receiver is on-hook, circuit is broken

-Battery at the CO

+

-

Loop

Tip

Ring

Signaling

• When receiver is off-hook, circuit is complete

• This is an example of loop start

-Battery at the CO

+

-

Loop

Tip

Ring

Signaling• This is an example of Ground start

• Off-hook signal accomplished by temporarily grounding the ring wire

• Stops GLARE

-Battery at the CO

+

-

Loop

Tip

Ring

PBX

Signaling over Analog Lines

• On-hook• Off-hook• Ringing– Ringing is sent using AC current rather than DC

When receiver is on-hook, circuit is broken

1 2

0%0%

1. True2. False

Additional Signaling

• Dual tone• Busy• Ring back• Congestion• Re-ordering• Receiver off-hook• No such number• Confirmation• And more

Address Signaling

• Pulse (70% connected and 30% broken connection)

• DTMF (dual tone multi-frequency)

DTMF works on

1 2 3 4

0% 0%0%0%

1. Only analog phones2. Only on digital phones3. Both analog and digital

phones4. Neither analog or

digital phones

What Did We Learn?

• What is analog connectivity

• Electric wave forms

• Understanding Analog signaling

Historical Voice

• Problems with Analog connection

• Converting Analog to Digital

• Converting Digital to Analog

Wiring a Problem

• Distance is prohibitive for analog wiring• Requires -2 wire system

Repeater Repeater

CO

Analog phone wiring requires

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1. One wire2. Two wire3. Three wire4. Four wire

Sample Voice

• Nyquist: If you sample at twice the highest frequency, you can accurately reconstruct a signal digitally

• Common frequencies:– Human hearing 20-20,000Hz– Human speech 200-9,000Hz– Nyquist therum 300-4000Hz

Quantizing the Sample

PAM – Pulse Amplitude Modulation

Human hearing range is 20 - 20,000Hz. Nyquist theory is what range?

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1. 20 – 20000Hz2. 200 – 20000Hz3. 200 – 9000Hz4. 300 – 4000Hz

Convert the Sample to Binary

• A-Law• U-Law (US, Canada, Japan)

• 0110011• Both use the first bit to represent “+” or “–” amplitude• A-Law uses “1” for Positive and “0” for negative• U-Law uses “0” for Positive and “1” for negative• Both use the next three bits for segments• Both use the following three bits for the interval• U-Law is known as Transcoding

Consider the bit string 1011011… This represents a positive notation for ___

1 2

0%0%

1. A-Law2. U-Law

Once in Binary

• Optionally compress the Samples– Send all the samples– Send just the changes– Build a code bank

*standard voice sample: 64kbps (G.711)*common compressed value: 8 kbps (G.729)

Which codec provides the best QoS?

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1. G.7292. G.7263. G.7234. G.711

What did we Learn?

• Problems with Analog connection

• Converting Analog to Digital

• Converting Digital to Analog

Multiple Calls on a single Pair of Wires

Solve the wiring problem: TDM

Understand T1, E1, and CAS specifications

Understand T1, E1, and CCS specifications

TDM• Carries multiple conversations over a 4 wire path• Build wire channels called DS0s• Each channel gives a time slot to transmit• Common DS0 Groups:

– T1 (24 DS0 frames)– E1 (32 DS0 frames_)

PBX PBX1 2 4 1 2 4 1 2 4

1 2 4

Analog Signals are Electrical Frequencies

• Once voice is digitized – signals must be 1s & 0s

• There are two methods:– CAS (Channel Associated Signaling)– CCS (Common Channel Signaling)

CAS in a T1 Environment (RBS) Robbed Bit Signaling

• The least significant bit in each 6th frame is signaling

Frame Channel Channel Channel Channel - - - Channel

1st 2nd 3rd 4th - - - 24th

1 DS0 DS0 DS0 DS0 DS0 fDS0

2 DS0 DS0 DS0 DS0 DS0 DS0

3 DS0 DS0 DS0 DS0 DS0 DS0

4 DS0 DS0 DS0 DS0 DS0 DS0

5 DS0 DS0 DS0 DS0 DS0 DS0

6 DS0s DS0s DS0s DS0s DS0s DS0s

The previous chart represents ____ in a T1 environment

1 2 3

0% 0%0%

1. CCS2. RBS3. SS7

Quality and Robbed Bits

• The 6th frame missing a bit degrades quality• T1 can send Large frames of 193 bits at a time• T1 Frame bit is in the first bit in DS0 24• T1 has two framing types:– Super framing (SF): sends 12 T1 frames at a time– Extended superframes (ESF): send 24 T1 frames at a

time• F6, F12 and F18, F24 (frames referenced as “A,B,C,D”)

CAS in an E1 Environment

• CAS has dedicated frames and signaling in separate channels

• CAS E1 has 32 channels• Ch1 – dedicated to framing• Ch17 – dedicated to signaling• Chs 2 - 16 and 18 - 32 are dedicated to voice• E1 is contra-intuitive ; called CAS since each time a slot is

signaled it matches to a voice channel• It is compatible with T1 CAS (has the same ABCD

signaling format

Bundling Channels Together on a T1 and E1 Connection

• CCS (Common Channel Signaling) is simpler than CAS• CCS dedicates a signaling channel on T1 and E1• Allows for the use of a signal protocol rather than just four

bits of signaling per channel– Allows for more clmplex signaling messages– Allows for proprietary signaling messages– Most common signaling protocol is ISDN’s Q.931– Other signaling protocols exist such as SS7

• Signaling Channel:– T 1 signaling channel 24– E1 signaling channel 17

What Did We Learn?

Multiple Calls on a single Pair of Wires

• Solve the wiring problem: TDM

• Understand T1, E1, and CAS specifications

• Understand T1, E1, and CCS specifications

PSTN

• Components of the PSN

• Difference between PBX and Key Systems

• PSTN Numbering Plans

PSTN Components

• Analog telephone• Local loop• Central Office (CO)• Trunks (SS7)• Trunks (CAS)• PBX• Digital Phones

Trunks

Which of the following is not a PSTN component

1 2 3 4 5 6 7 8

0% 0% 0% 0%0%0%0%0%

1. Analog telephone2. PBX3. CAS Trunks4. Router5. SS7 Trunks 6. Central office7. Local loop

Offices

• PBX and Key Systems– Typical digital PSTN connection (T1 & E1)– Provide each user unique extension number– Support a large number of features

• Key Systems– Typically Analog PSTN connection – Users share lines between phones– Support smaller number of features

PSTN Dialing Plan

• PSTN number plan managed under ITU-TE-164 standard• Country• National description code• Subscriber number

North American Numbering Plan (NANP)• Country code• Area code• Central office code• Subscriber code

• 1-555-510-3001 (NANP)

Country code - Area code - Central office code - Subscriber code

This numbering plan represents

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0% 0%0%0%

1. E.1642. NANP3. Both4. None of the above

What Did We Learn?

• Components of the PSN

• Difference between PBX and Key Systems

• PSTN Numbering Plans

Cisco Components of the Voice Networks

• Cisco infrastructure model

• Cisco Call Processing

• Cisco applications options

The Infrastructure Model

Call Processing: UC500

• Supports 8 to 48 IP phones• Integrated Voice main and Auto-attendant• External MOH• FX0 modules for external Analog phones• FX1 modules for analog phone connections• Routing/NAT support support• VPN support • Opt 802.11 wireless

Step above UC500 – CME

• Supports more features than UC500• Voice mail support added through (CUE) Cisco

Unity Express• Runs on Cisco ISRs• Mostly CLI configuring

Infrastructure Parts

1 2 3 4 5

0% 0% 0%0%0%

1. End Points2. Hardware 3. Applications4. Infrastructure5. Call processing

Cisco RoutersCisco Max IP phones Max SIP phones

2801 25 25

2811 35 25

2821 50 50

2851 100 100

: :

3845 250 250

Business Edition

• Provide scalability to 500 IP phones• Combines three applications into one– CCM (Cisco Communications Manager)– Cisco Unity Communications– Cisco Unified mobility

• Fantastic but NO REDUNDANCY

Full Blown Call Manager (CUCM)

• Scales to 60,000 IP phones per cluster• Multi-server redundancy• Multi-site support• $$$

Applications• Cisco Unity Express up to 100 users

– Network module (NM) an advan integration module (AIM)– Lenix based, IVR, Voicemail from email, WEB, phone

• Cisco Unity Connection up to 500 users– 7500 users with dedicated servers– Advanced call routing rules– NO redundancy

• Cisco Unity (7500 users per server)– Integrated with Microsoft Exchange, lotus notes, Novell

Groupwise– Redundant multiple servers

Other Applications

• IVR (Integrated Voice Response)• Unified Contact Center Express• Unified Meeting Plan• Unified Mobility• Emergency Responders

What is the problem with a UC500

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1. No unified mobility2. No analog phone support3. No redundancy4. No unified communications

What Did We Learn?

• Components of the PSN

• Difference between PBX and Key Systems

• PSTN Numbering Plans

The End