1. The transmission of a signal or combination of signals intended to trigger a response.
2. The process whereby a station or device requests another station or device to identify itself or to give its status.

A suspension of a process, such as the execution of a computer program, caused by an event external to that process, and performed in such a way that the process can be resumed. Synonym interruption.

Modulation in which there is on-off keying of a continuous wave.

Synonym isochronous burst transmission.

Synonym interrupt.

A system that monitors a pilot for interruptions on frequency division multiplexing (FDM) systems and that transmits an indication to the switching equipment. [T1.110-1987]

A single direct transmission channel, e.g., voice-frequency circuit, between switching nodes.

1. In a digital transmission system, distortion of the received signal, which distortion is manifested in the temporal spreading and consequent overlap of individual pulses to the degree that the receiver cannot reliably distinguish between changes of state, i.e., between individual signal elements.
Note 1: At a certain threshold, intersymbol interference will compromise the integrity of the received data.
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Circuits between toll centers and circuits between a toll center and a tandem system in a different toll center area. [47 CFR Pt.36-A]

A single direct transmission channel, e.g., voice-frequency circuit, between two toll offices.