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Home Telephone Exchange Service and Systems Line Switches
 
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Line Switches

The line switch is a switch connected to each subscriber line and has access to a number of trunks to succeeding switches in the step-by-step system. This line switch operates automatically when the calling party raises the handset or the receiver, and it connects the calling line to a trunk leading to an idle selector switch (or connector switch in small installations). These switches are referred to as non-numerical switches because they do not require dial impulses for their operation. There are two common types of line switches: (1) the plunger type with associated master switch and (2) the rotary type.

The plunger line switches are arranged in groups of 25 to 100 line switches under the control of one master switch and have access to ten trunks to selectors (or connectors). The plunger line switch consists of a slow-operate type of line relay and an operating magnet which actuates a pivoted plunger. This plunger may engage any one of ten sets of bank contacts connected to trunks leading to selectors. The master switch keeps the plungers of all the idle switches of the group resting opposite an idle trunk; therefore, the master switch preselects the trunk before the call is initiated.

The rotary line switch is sometimes used instead of the plunger line switch. A rotary line switch is associated with each line and is entirely independent of any other rotary line switch and, therefore, does not require a master switching mechanism. The rotary line switch consists of a set of wipers which is rotated over a semicylindrical bank of contacts by means of a magnet-operated rachet mechanism. Each rotary switch has an associated relay assembly consisting of a slow-operate type of line relay and cutoff relay.


Home Telephone Exchange Service and Systems Line Switches

Last Update: 2011-05-30