I've got a radio telephone repeater with an analog line to an FXS port on a EVM-HD module in a 3825 controlled by CM6.1 using MGCP. Radio users can make and receive telephone calls this way. The problem is CM sees some of the DTMF tones as multiple key presses. If the person presses a '5' CM will see it as '55' about half the time. So dialing 5551212 might be read as 5555122. The radios worked fine on a Nortel PBX but CM just isn't reliably getting the digits correctly. Outbound calls from a phone to the radios work fine. There are several possible causes but I believe I can work around the problem by adjusting some timing in CM or the router. I would like to set a minimum "off" or "no keypress" parameter so that a tiny gap between digits isn't registered as the end of one DTMF tone and the beginning of another. (I'm suspecting there are small dropouts in the radio signal.) I'd like to set something like a minimum of 100ms or so of dead air before CM recognizes the keypress is done and is ready for the next DTMF tone.
I am going to try this using an ATA-186 just to see if the different hardware responds differently.
Has anyone experienced this and have a solution? Or does anyone have a different idea on the cause and solution?