atcomsystems.ca/forum Forums Wiring - Telecom Carriers - Trunks & Services Telephone Repairs & Equipment Viking AR-1 (autoattendant) incompatibility with cellphone gateway

OK, I did some tests and I was wrong: the touch tones I heard were from the cell to the remote, but the remote phone could not dial DTMF tones and have them heard by the cell phone.. at all.

I was able to take the Xlink and the Viking units out of the equation completely, and found that just between the cell phone and a land line, the cellphone's touch tones /could/ be heard by the land line, but the land line generated tones were being removed from the voice call, presumably by the carrier.

So for instance if you have a cell phone and a land line, try calling the cell from your land line, and try generating touch tones from the land line and see if you hear the tones on your cell. In my tests the tones were magically deleted and could not be heard..! But vice versa worked fine.

My experiments seem to show the tones don't make it through; it's a one way problem, where the remote phone can't send touch tones to the cell.

I tried that test with two different cell phones each on different carriers -- same problem. My cell (on AT&T's cell network) talking to an analog line, and using my friend's cell (on Verizon's cell network) with the same behavior: Touch tones generated by the remote analog phone simply would not pass through to the cell phones.

I investigated this a bit, and I think it might get into the details of analog-to-digital encoding, where DTMF sequences are /parsed/ during analog-to-digital, sent as separate digital data representations of the tones, and those are RE-generated at the other end where digital is converted back to analog. This way the tones won't be mangled by audio compression, and transmit clearly over otherwise noisy or imperfect networks (such as wireless or VOIP/internet), by having the tones transmitted as more reliably as digital representations of the tones, and regenerated at the D->A end.

It seems like this is an "issue" with the carrier, or possibly the cell phones (not sure which). Either the carrier is "eating" the DTMF tones transmitting the digital representations but the cell is not converting those digital messages back into DTMF, or the carrier is eating the DTMF and NOT transmitting the digital representations, possibly parsing the tones for their own purposes. Either way, the tones are being removed from the voice circuit completely.

Anyway, my tests removed the Viking and Xlink equipment from the equation, making it clear it wasn't related at all to that equipment; the problem is the tones aren't making it through the phone connection.