A busy circuit is a tone of two combined frequencies that lasts for .5 seconds and repeats after .5 seconds of silence.

Question

Quizplus · Accepted Answer

A busy circuit tone, or busy signal, typically consists of a repeating tone on and off to indicate the line is in use, but the specific description of two combined frequencies lasting for .5 seconds and repeating after .5 seconds of silence does not accurately describe all busy signals, as the exact pattern can vary by country and system.

A Busy Circuit Is a Tone of Two Combined Frequencies