Communications Review

RA # 9292 - Electronics Engineering Law of 2004; April 17, 2004; Effective May, 2008
Communications is the process of sending and/or receiving data, signals, and/or messages between two or more points by radio, cable, optical waveguides, or other devices, and wired or wireless medium.

The goal of communications system is to transfer information from one place to another.

Classes of Communications System:
Simplex
Half-Duplex
Full-Duplex

Inventions:
Telephone - 1876
Radio - 1894
TV - 1945
Internet - 1994, Sputnik

Telephony:
1st - used bell, speaker, and earpiece
It was called Butterstamp telephone
Rotary-dialed phone - 500 type telephone set; pulse dialing
Push-button dial phone - 2500 type
Modern telephone set - uses caller ID

There were only 6 telephones back then.
1st patent - Alexander Graham Bell
telephone switchboard - Tivaidar Puskas
1st patent for caller ID - Theodore George Paraskevakos (Athens, Greece)

PSTN - public switched telephone network; generic term for domestic public telephone network; largest and best known traffic network
network - system of interconnected elements
telecommunications network - network of interconnected elements designed to carry telecommunications services
traffic - flow of messages

2 compositions of PSTN:
inside plant
outside plant

CPE - customer premise equipment; not part of PSTN because it is private, therefore not part of the network

Types of CPE:
telephone set
modem
PBX

Transmission facilities:
lines - communications path from CPE to SO (switching office)
trunk - connection between two switching offices.
special service curcuit (SSC) - provides special service to specific customers

*POTS - plain old telephone system
*switching office - also called central office; provides connection between customer line and switching facilities
*tandem office - an exchange without loops connected to it. The only facilities connected to the switching machine in a tandem office are trunks.

When a subscriber initiates a long distance call, the local exchange connects the caller to a toll office through a facility called a toll-connecting trunk (interface toll trunk).

Area codes/country codes are used because tandem offices are only used for local calls.

IGF - international gateway facility