Telephone Exchange Service and Systems

A telephone exchange^ref.1 is a "telephone system for providing telephone communication within a particular local area, usually within or embracing a city, town or village, and environs." Service within an exchange is usually rendered at a fixed monthly rate or on a metered basis.

In a telephone system, the various lines are switched at the central office, defined^ref.1 as "an office in a telephone system providing service to the general public where orders for or signals controlling telephone connections are received and connections established." A telephone exchange serving a small community may have only one central office and thus is a single-office exchange.^ref.1 For large towns and cities_; more than one central office is needed, requiring a multioffice exchange.^ref.1 The offices just mentioned are local central offices, defined^ref.1 as "a central office arranged for terminating subscriber lines and provided with trunks for establishing connections to and from other central offices."

The trunk^ref.1 mentioned in the preceding paragraph is a "telephone line or channel between two central offices or switching devices, which is used in providing telephone connections between subscribers generally." By means of interoffice trunks,^ref.1 a call that originates in one central office can be passed to another office for completion.

The telephone customer or subscriber^ref.1 is provided with a telephone set.^ref.1 A telephone station^ref.1 is a telephone set and associated wiring and apparatus installed on the subscriber's premises. A telephone set is sometimes called a subscriber set or subset. Telephone sets are of two general types, local-battery telephone sets, and common-battery telephone sets.