Behaviour of Voice Activated Recording (VOX) (Summarise in point form)

VOX recording in telephone recorder is similar to your cassette recorders of the same function where eventhough recording is enabled, the recorder doesn’t record until it hears a sound loud enough to trigger the start of recording. An example would be when you pick up the phone and start dialing or talking. The ON threshold level and duration will determine when the start of recording is triggered. The threshold level usually has no unit of measure and is normally configured by trial and error because you have no easy way to measure the audio level anyway. The ON duration is usually in seconds so that unwanted noise spikes will not false trigger recording unnecessarily.

The OFF threshold level and duration will then decide when the recording should end. To simplify configuration, some telephone recorder make OFF threshold = ON threshold so that you have 1 less thing to configure. When you set OFF duration to 5 seconds, it means that if both person should pause during a conversation for more than 5 seconds, the recorder will stop the recording. This means that 1 phone call can end up with more than 1 recording file. When you set OFF duration to 15 sec, it means that if you make another call within 15 sec from the earlier call, the 2 calls will be recorded as 1 call.

Even nowadays where the latest Digital Channel recording hardware is concerned, I have realized that some PABXes supported by our competitor’s cards works in VOX mode only. This is because the digital decoding was done for voice data only but not for signaling data. Without decoding signaling data, the telephone logger is not able to know the exact time when you pickup and hangup on the phone.