AT&T 2500 series, 7500 series, 7100 series, 7200 series, 7400 series, 7300 series Types of Networks

2-2COMMUNICATION SYSTEM NETWORKING — AN OVERVIEW

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TYPES OF NETWORKS

The type of network you install depends upon the geographical distribution of the network nodes, the capabilities you need in each node, and the relative cost of each networking alternative. To satisfy these variables, you can install any of the following network types.

∙Tandem tie trunk (TTT) network — A network of switches linked by dial-repeating trunks. In this type of network, calls are not automatically routed to the final destination. To call a distant switch, the user steps the call through all the switches in the connection by repeatedly entering the dial access code (DAC) of the trunk group to the next switch as soon as he or she receives dial tone from the newest switch along the path. When all the switches in the connection have been traversed, and a connection is made with the destination switch, the user dials the extension number.

SWITCH 2	SWITCH	SWITCH 3	SWITCH	EXTENSION	SWITCH
DAC	1	DAC	2		3

∙Main-satellite/tributary (MS/T) network — A network of switches in which one switch is designated as the main, while subtending switches are satellites or tributaries. The main switch is fully functional; each satellite uses the trunks and attendants at the main switch. Tributary switches differ from satellite switches in that they have their own listed directory number and may have their own attendant and public network facilities. MS/T users reach other users by dialing their extension numbers.

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SATELLITE

∙Electronic tandem network (ETN) — A network of switches in which one switch at each location is designated as the tandem switch, through which all communications must travel to reach the tandem at another location. Switches that communicate with the tandem at the same location are called main switches. ETN switches reach other nodes in an ETN by sending a location code, followed by an extension number and, sometimes, a traveling class mark (TCM).