Comcast Digital Voice Problem with Old Phones

[Doug]

When hooking up the cable modem with Digital Voice, some Older Bell, And ATT phones will not generate DTMF tones to dial. This is because the phones have DIODE protection built in.

When the telephone connecting cord from the cable modem is plugged into the house circuit, it causes reverse polarity to the house wiring.

This may be solved by removing one of the connectors on the phone cable then inverting the new connector so the red and green wires are switched, thus curing the reverse polarity.

It may also be solved by connecting the telephone modem cable and cable to the house wiring to a 2 line splitter.

When both lines are on the same side of the splitter the polarity will be reversed.

This may also solve the problem with having to hard wire alarm systems to the modem.

The ideal solution would be to have all of the cable modems provided with a polarity switch on the back of the cable box.