Telephone Exchange - Technologies

Technologies

This article will use the following terms:

• manual service for a condition where a human operator routes calls inside an exchange and a dial is not used
• dial service for an exchange where calls are routed by a switch interpreting dialed digits
• telephone exchange for the building housing the switching equipment
• telephone switch for the switching equipment
• concentrator for a device that concentrates traffic, be it remote or co-located with the switch
• off-hook for a tip condition or to describe a circuit that is in use (i.e., when a phone call is in progress)
• on-hook for an idle circuit (i.e., no phone call is in progress)
• wire center for the area served by a particular switch or central office

Many of the terms in this article have conflicting UK and US usages.

• central office originally referred to switching equipment and its operators. Now it is used generally for the building housing switching and related inside plant equipment.
• telephone exchange means an exchange building in the UK, and is also the UK name for a telephone switch, and also has a legal meaning in U.S. telecoms.
• telephone switch is the U.S. term, but is in increasing use in technical UK telecoms usage, to make the CO/switch/concentrator distinction clear.