Voice operated exchange
A Voice Operated Exchange (VOX, also obsolete voice scales ) is a voice-controlled switch.
This activates the send / receive switchover in radio devices or starts recording in the case of sound recordings. A VOX saves switching by hand with push-to-talk (PTT) and is therefore used in hands-free systems , for example .
The voltage level at the microphone is evaluated and the PTT signal is generated when an adjustable threshold is exceeded. This will automatically switch the radio to transmit when you speak loud enough into the microphone. Unintentional radio transmission is possible due to background noises or conversations that overcome the response threshold. Unintentional triggering by the received signal emitted by the loudspeaker can be prevented by an additional circuit (Anti-VOX). Another disadvantage is that the VOX takes a short time to respond, i.e. the device is only switched on with a delay.
In order to bridge short pauses, the PTT signal only drops out after a certain delay time (VOX delay).
literature
- Joseph J. Carr: The TAB Handbook of Radio Communications. TAB Books, New York 1984, p. 557.
Individual evidence
- ^ Herbert Petzoldt: Counter and intercom systems , Fachbuchverlag, Leipzig 1952.