System iNetwork

Gentle User,
Dr. I Doctor will have to play Solomon in reverse to solve your problem. Fortunately, it is one that has become common enough lately that the cause is easily determined. Alas, Dr. I Doctor cannot promise as much for the solution.

The cause of the problem is your LEC, which has almost certainly made a change to its system to which it's unwilling to admit. Small and large businesses aren't the only entities that recognize the economics of VoIP. Many LECs thirst for the savings VoIP promises in reduced bandwidth and cheaper infrastructure; your LEC is likely one of them. All over the country, LECs are switching their internal voice transport from the traditionally reliable, but fairly expensive, circuit-switched (CS) network to much cheaper Internet Protocol (IP) networks.

Your LEC is not routing your phone calls through the Internet. That would be truly awful, given the vagaries of Internet routing and congestion. However, the LEC is routing your calls through its own internal private IP network, which is much less costly to maintain than the old CS network. Theoretically, this shouldn't be a problem — the LEC still accepts analog calls and digitizes them for transport over IP, just as it did with its CS network. Calls originating on ISDN or T1 digital trunks are digitized by the customer before they get to the phone company, so they are not affected by this change.

But with your VoIP system, calls are digitized in your phones, then sent to the POTS gateway where they are converted to analog signaling, then routed to the LEC, which redigitizes the signal for IP transport. It's the intermediate conversion to analog that's causing difficulties; this conversion often frustrates the echo-cancelling technology normally built into your phone system. The LEC's intermediate digitization step causes enough signal degradation to prevent echo recognition, so echoed voices that would normally be canceled get through to the end user.

The unfortunate news is that you likely can't fix this and still use POTS lines with your VoIP PBX. You might have the VoIP vendor try adjusting your PBX echo cancellation settings, but that usually won't remedy the problem for all calls. Your best bet is to bite the cost bullet and simply make local calls through your ISDN PRI lines, which are immune to this particular malady.