a visual decoding of telephony history
Post on 19-Feb-2017
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Part 02 / 03
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Exchanges the control information
associated with the caller.
SIGNALING SYSTEM (SS7)
Signal Pathways
A dedicated signaling channel is
maintained alongside an active voice
channel where the conversation lives.
COMMON CHANNEL
SIGNALING (CCS)
Analog signals are transmitted
through electrical wires, resistors
and capacitors.
EARLY TELEPHONE
Large transmission lines are used
for long-distance calls.
PSTN: Publicly Switched Telephone Network
TDM: Time Division Multiplexing
Time slots
are assigned to
single users
TRADITIONAL TELEPHONY
ACROSS PSTN* & TDM*
Single unbroken line from telephone
A to telephone B in classic PSTN.
CIRCUIT SWITCH NETWORK
Data stream is split into small
packets that are sent on router-
determined pathways.
PACKET SWITCHED
NETWORKS (PSN)
Digital signals are transmitted by
passing 8000 analog samples through
a computer chip.
MODERN TELEPHONE
Pressable phone numbers emit high
and low-frequncy sine waves.
DUAL TONE MULTI
FREQUENCY (DTMF)
Life of a Call
MODERN TELEPHONY
TECHNOLOGY
Signal Transmission over the Ages
Voice & Data
Once Separate
Computer files and voice signals are
transmitted over the same wires.
Voice Data
Digital Subscriber Line (DSL)
This is accomplished by keeping the
basic PSTN infrastructure and placing
data transmission on top of it.
OLD UNIFICATION METHOD
Voice Over Internet Protocol (VoIP)
Voice, data, and video are transmitted
over networks in packets (PSN) rather
than dedicated timeslots (TDM).
NEW UNIFICATION METHOD
Noise is additive and
therefore vulnerable to
interference and degredation
Noise is regenerated
through sampling and
therefore more clear
Now United
Signaling Channel
Voice Channel
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