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FIIG:  T187-B

Entry Date:  Apr-01-1974

Concept:  

Status:  A

Applicability:  BB

Type:  0

Definition:  A rack, part of a telephone central office, on which the relays and elements of various telephone central office circuits such as trunk and line circuits, and miscellaneous testing and alarm circuits are mounted. The rack is stocked as a completely wired and equipped unit. Excludes: items on which strowger or stepping switches are mounted. Do not use if a more specific item name can be found in this index. See also SHELF, TELEPHONE SWITCH; and RELAY ASSEMBLY.

Basic INC:  70595

Basic Name:  RELAY

Description:  1. (Electrical) A protective or control device which completes or breaks an electrical circuit in response to electrical changes in an external circuit. The contacts and actuating element are not in series. It is not designed to permit manual opening of the protected or controlled circuit but may have facilities for manual closing or reset upon automatic opening of the circuit. It is classified by the type of contact actuation, such as armature, meter movement, motor driven, rotary, and solenoid rather than by its application. Such uses as time delay, antenna switching, and keying are secondary features since, for example, a time-delay relay may be of the armature, motor driven, solenoid, or thermal type. MOTOR-DRIVEN SWITCHES, PHOTOELECTRIC TUBES, AND ELECTRON TUBES WHICH MAY FUNCTION AS SWITCHING DEVICES ARE NOT CONSIDERED AS RELAYS. For items with provisions for manual operation, see RELAY-SWITCH. For items in which the contacts and actuating elements are in series, see CIRCUIT BREAKER. See also REGULATOR, VOLTAGE; REGULATOR, CURRENT; SWITCH (as modified); and TIMER, SEQUENTIAL.