TP4 COS usage instead of VOX usage

I am attempting to connect Digirig to a radio that does not have a pre-made cable and will need to make a homemade cable. One of the things that I would like to use is a COS (Carrier Operated Signal) for when the Digirig should use the audio instead of VOX. In looking at the schematic I see that TP4 is COS and does not come out to either 3.5mm jack.

Here is the big question → Can I apply either an active Hi or Active Low signal to this TP4 point in order to eliminate VOX usage? If not does anyone have a way to set this up for COS usage as compared to VOX usage?

Depending on the radio you are using, there is one or two good PTT methods available with Digirig before we even consider VOX as an option. PTT by RTS is always available and there’s also PTT by CAT for capable radios.

What radio and what software do you plan to setup?

Motorola XTL, APX, or XPR series; EF Johnson 5300 series; Kenwood VM/NX series; and some other commercial brands.

PTT from the Digirig to the mobile is not so much the concern but more so using the COS/COR generated from the radio to signal the digirig to use the audio on the input lines.

The software I am using offers the following for USB input (radio to PC): CTS, DSR, Ring, or CD and can either be set to High or Low. How would I wire the radio then to the Digirig and would I need to use SERIAL side?

Appreciate the help as being a newbie here I am trying to learn.

Digirig’s audio is fully duplex and the input is continuously accepting the incoming signal even during transmission. I must be missing something, but I don’t quite understand the need to switch the inputs on and off.

I do see the need for something like this in the analog repeater where the incoming signal detected by one radio triggers transmit in another.

VOX is NOT an effective way to provide a constant level of audio into something. If a pause in the audio occurs the VOX will cut out. This is especially true with digital voice coming out of the speaker.

I need to find a way that when a radio can provide a COS that it will cause the digirig to listen to the audio input to the digirig. Many radios do offer some sort of COS or COR output for wiring into controllers or linking devices.

Therefore, asking again does TP4 (labeled as COS on the schematic) allow either an active hi or active low to be applied to eliminate the Vox aspect.

Application is NOT data but voice and having VOX injects issues and is problematic as stated. S2E8 - (On the Tech Bench) Interface for PTToC - YouTube

I see the COS being useful in audio applications. The CM108 pins that are routed to Digirig’s through hole connections are GPIOs of the audio codec - they are general purpose inputs and outputs. In the Allstar interfaces these pins are driven by the software to implement CTCSS, COS and PTT functionality.


If the system you are implementing needs these signals and the software knows how to set/get these lines in CM108 then you can make use of them. The easiest way to route the additional signals outside is to bridge the corresponding through-hole to one of the solder jumper pads. For example if you need COS and don’t use 3.3V out (only needed for TX-500 radios) you can make this connection:

This will route COS to the R2 of the socket labeled “serial”.

We can look at the specifics of the software and hardware you are using to determine what maximum functionality can be implemented using Digirig.

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