Comparison With Push-to-talk
Unlike push-to-talk (PTT) operation, VOX is automatic; the user can keep his hands free while talking. But VOX also has some significant disadvantages that explain why PTT is still common.
Most VOX circuits have a sensitivity adjustment, but unwanted (and sometimes undetected) VOX triggering can still occur on background noise, heavy breathing or a side conversation. Conversely, it may not activate when desired on speech that is too weak.
The VOX in a two-way radio can also be triggered by the loudspeaker carrying the other side of the conversation. This problem can be minimized with an "anti vox" feature to decrease VOX sensitivity when the receiver is active.
Transmitters and recorders have short but finite activation times that may clip the beginnings of phrases. Some modern VOX circuits eliminate this problem by recording or transmitting a delayed version of the input signal.
VOX uses a "hang" timer, typically 1-3 seconds, to remain engaged during brief speech pauses. This means the last several seconds of each transmission or recorded segment are always silence. A VOX-activated recorder can delete the end of each segment but the user of a VOX-activated half duplex radio must wait for the timer to expire before he can receive again.
Read more about this topic: Voice-operated Switch
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