An operating condition of a clock in which its local oscillator is not locked to an external synchronization reference, and is using no storage techniques to sustain its accuracy. [T1.101-1987]

An operating condition of a clock that has lost its controlling input and is using stored data, acquired while in normal operation, to control its output. The stored data is averaged to minimize the effects of short-term variations, allowing the normal conditions to be simulated within specifications. Holdover terminates when the output of the clock is no longer controlled by… (Read More →)

An operating condition of a clock in which the output signals are controlled by an external input reference. It is the expected mode. In normal mode, each clock in a chain has the same long-term average frequency, and the time error between the input and output of each clock is bounded. Only stratum 1 sources of timing require no input… (Read More →)

The rate of relative phase change between a given clock signal and a stable reference signal.
Note: The two signals are generally at or near the same frequency or have an integral multiple frequency relationship.

The rate at which a clock issues timing pulses.
Note: Clock rates are usually expressed in pulses per second, such as
4. 96 Mp/s (megapulses per second).

The maximum permissible departure of a clock indication from a designated time reference such as Coordinated Universal Time (UTC).

A track on which a pattern of signals is recorded to provide a timing reference.

Synonym right-hand (or clockwise) polarized wave.

In broadcast and cable television, the insertion, into the blank lines between frames, of information that may be decoded and displayed on the screen as written words corresponding to those being spoken and transmitted via the conventional audio subcarrier.
Note: Closed captioning, developed for the hearing-impaired, requires a special decoder, which may be external to, or built into, the television… (Read More →)

1. In radio and television transmission, pertaining to an arrangement in which programs are directly transmitted to specific users and not broadcast to the general public.
2. In telecommunications, a circuit dedicated to specific users.
3. A completed electrical circuit.