1. In frequency modulation, the rest frequency, i.e., the frequency of the unmodulated carrier. Synonym carrier frequency.
2. The frequency of the middle of the bandwidth of a channel. [47CFR]
3. In facsimile systems, the frequency midway between the picture-black and picture-white frequencies.

1. A common carrier switching center in which trunks and/or loops are terminated and switched.
Note: In the DOD, "common carrier" is called "commercial carrier. " Synonym switch. Other synonyms [loosely] end office, exchange, local central office, local exchange, local office, switching exchange, telephone exchange.
2. A switching unit, in a telephone system which provides service to the general public,… (Read More →)

The sub-NPA code in a TN, i.e., digits D-E-F of a 10-digit NANP Area address. Central office codes are in the form “NXX,” where N is a number from 2 to 9 and X is a number from 0 to
9. Central office codes may also be referred to as “NXX codes. ” (47 C. F. R. §
5
2.… (Read More →)

Loosely, in the sense of a trunk between public and private switches, a synonym for central office trunk. See trunk.

The first three digits (N) of the seven-digit telephone number assigned to a customer's telephone exchange service when dialed on a local basis. [NECA/FCC] Synonym [loosely]prefix.

Loosely, in the sense of a trunk between public and private switches, a synonym for central office connecting facility. See trunk.

See CPU.

Synonym CPU.

A function of a usually centrally located attendant console that permits the control of multiple switches, some of which may be geographically remote.

An automatic message accounting system that serves more than one switch from a central location.
Note: When using CAMA, human intervention may be required.