Implement VOX in a bridge or channel driver?

I have inherited a program that uses asterisk 1.8 to interface between SIP and a radio. I am pretty new to Asterisk. The existing system uses a custom channel driver to communicate to the radio. This channel driver code includes a Buffer and a VOX analysis to know when the SIP user is talking, thus signaling to key up the radio when a noise is detected.

We are upgrading to V16 and the existing custom channel drivers are being removed and replaced with a commercial E&M board which has its own channel driver. The board has some VOX triggering capability, but it is not working as expected and it might just be easier at this point to put our VOX and buffer in the new channel driver. But, would it make more sense to put it in a new bridge and then use the VOX bridge and the regular bridge to link the calls? ONce again I am pretty new to this.

IS there any existing VOX and buffer implementations in Asterisk or third party?

Nowadays VoIP is basically SIP + some Web technologies. You would harldy find anybody here who still has the knowledge to help you. But you could describe more precisely what the system looks like and what you are trying to achieve. I couldn’t figure out what you mean with “radio” and “VOX analysis to know when…” That sounds a lot like POTS, but you don’t need that anymore.

Maybe all you need is an ATA device, or maybe a simple PA (public address) box, but from the given info I couldn’t figure it out.


We have all hardware we need. I am just trying to determine, in source code, if we should implement a VOX inside of our new channel driver, or if it would be better to put the code in another Asterisk module and use the dial plan to chain the two bridges together.

What is a “VOX”? I haven’t seen this term in this context here before.

VOX is “voice operated switch”. Simple radios, e.g. walkie talkies are half duplex, meaning they can only do one of transmit or receive at the same time. They also typically share as single frequency channel with other users (e.g. other taxis in a taxi system. That means that you only want the transmitter active when someone is actually speaking. That can either be done by push to talk, where a button is pressed to transmit, or by VOX.

Actually one way of dealing with echo, especially with speaker phones, even for SIP phones is to use VOX (although you’ll then also use anti-VOX, so that incoming speech will make the system less sensitive to local sounds).

Whilst this sounds like the OP was paying for professional equipment, this sort of telephone patching is also done by radio amateurs, especially in the US, where third party traffic rules are less strict, and some appear to use Asterisk, so it is not impossible that the OP will get a reply, however, the number of regular contributors here is rather small, so he’d have to be rather lucky.

David, Correct, I have professional radios and E&M connections to them. This was more of a software development question regarding channel drivers and bridges. Is there a better forum for the SW side of asterisk?

However, I suspect this may be an area where there is little expertise.

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