What is "off-the-air"

In telecommunication, the term off-air or off-the-air has the following meanings:

1. In radio communications systems, pertaining to a radio station or television station that is completely shut down, i.e. that is not transmitting any signal, not even an un- modulated carrier wave. Other terms in this context include "dark" or "silent", though those terms were typically used for a station that has left the air for an extended period of time, or permanently; while "off-the-air" is generally used for a brief period of time, or for a station that has recently stopped broadcasting.
2. In a radio station, pertaining to a particular source of modulation, such as a specific microphone, that is disconnected, i.e. is no longer capable of modulating the carrier.

Note: The carrier wave may continue unmodulated or it may be modulated by another signal source, such as a subcarrier.

Also, off-the-air may be synonymous with over-the-air or from-the-air, as in picking up a terrestrial broadcast TV station off-the-air instead of from cable TV. As this usage may be confusing due to the term's other meanings, the terms "over the air" or "on the air" are more standard in the broadcasting industry.