This slide presentation is a HTML version of a lesson plan originally
built in Macromedia for CDA-2502
by L. Scott
Freudenthal. It is intended to be presented in a classroom environment
with the accompaniment of a lecturer (i.e. Scott) and a ~52 inch monitor
(thus the large font selections).
Why are we studying the
Why are we studying the phone system?
The Phone system is the largest network in the World with over 170 million
Twisted Pair Fiber optics
Microwave Satellite links
Access on demand
What is a PBX?
Switching Device, may be analog or digital.
Reduces cables to Central
Internal calls handled internally.
Reduces dependence on phone company.
Faster than Analog.
Higher data rates.
- Call Back
- Call Fwd
- Least cost routing.
"Codec" - Coder-Decoder.
Digitized voice on digital phones.
May use analog devices witha digital switch.
Analog call requires 4kHz bandwidth, spaced by 4kHz.
Digital call requires 64kbps.
Codec digitizes at 8kHZ.
8 bits used to represent each sample.
8,000 samples x 8 bits/sample = 64,000 bps
-End to end digital network
1) PRI - Primary Rate Interface.
2) BRI - Basic Rate Interface.
Primary Rate Interface.
Interconnects switches with ISDN link.
Typically a T1 line.
23B + D
Basic Rate Interface.
Connects ISDN terminals (phones) to the switch.
Typically a twisted pair.
2B + D
What is 2B + D?
What is 2B + D?
2 - 64,000 bps clear channel
1 - 16,000 bps control channel
Simultaneous Voice and Data Calls
Automatic Call Distribution
Automatic Call Return
Automatic Database access / Voice Response
Analog phone lines: must convert digital data (computer)
into analog data.
Using switched digital end to end phone line, up to 64,000 bps.
Modem not required, data access (DSU) can be built into
Dedicated analog circuits.
Up to 19,200 bps
throughput with compression
Dedicated digital circuits.
64 kbps, usable 56
DS-1 : (T1) 1.544 Mbps (24 x DS-0)
DS-2 : 6.312 Mbps (3 x DS-1)
DS-3 : 44.736 Mbps (7 x DS-2)
DS-4 : 274.176 Mbps (6 x DS-3)
Variations, other data offerings:
Native LAN Link
FCCJ's Phone System
Northern Telecom Meridian
ISDN to every desk