In order to get a telephone call to travel from one
place to another, it must pass through the telephone network. This
network consists of many different parts, operated by many different
companies, but are inter-connected using common signaling methods.
This section will discuss Central Offices, signaling between
different telephone systems, different methods of transmission, and
the use of tandems (transfer) in the network.
Central Office Switching Systems in North America - Past &
Details and history on vintage (electro-mechanical), modern
(electronic & digital) and next-generation (packet-based
softswitch) telephone switching systems used in the North American
public switched telephone network.
Network Signaling Technology
Details on the signaling methods used within the North American
telephone network to allow central office and tandem systems to "talk"
with each other.
Network Transmission Technology
Details on the physical means on how a telephone call is handled
through the network between different systems.
Number 4 Crossbar (#4XB) List
A list of locations where AT&T Long Lines (Bell System) used the
Number 4 Crossbar (#4XB) Tandem system in the North American toll
network from 1940s until the 1980s.
Network Systems websites (off-site)
Central Office Online
A website dedicated to central office systems, both past and present.
Copyright 2008 Telephone World
Page last modified December 20, 2008
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