Accy conector voltage

[olderookie]

I have a project I am working on and I have a GM300 with a 16pin connector I am going to make another garage door opener.

I want to use the alert on the radio to open the garage door. I have the idea worked out in my head but I am not sure what kind of voltage and amperage I am going to see coming out of the radio.

The radio is actually part of a home brew repeater I inherited. I figure if I alert the transmit radio in simplex with DTMF and then the alert from the connector will trip a relay that closes the button circuit on the garage door button. I am not sure about the closure time but I believe the alert time will handle that.

I have seen posts where a similar idea has been used for remote start on a vehicle and I know that this concept is used for other things as well, opening fire station doors.

anyone got any questions comments insults etc come on with it.

thanks
Joe