Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!accuvax.nwu.edu!nucsrl!telecom-request From: Brian Kantor Newsgroups: comp.dcom.telecom Subject: Re: Loop Start and Ground Start Trunk Supervision Message-ID: <6196@accuvax.nwu.edu> Date: 9 Apr 90 15:42:54 GMT Sender: news@accuvax.nwu.edu Reply-To: Brian Kantor Organization: The Avant-Garde of the Now, Ltd. Lines: 27 Approved: Telecom@eecs.nwu.edu X-Submissions-To: telecom@eecs.nwu.edu X-Administrivia-To: telecom-request@eecs.nwu.edu X-Telecom-Digest: Volume 10, Issue 242, Message 5 of 9 Our Ericsson MD-110 switch seems to have at least two types of analog line interfaces: one does not provide loop supervision to the called extension when a callER disconnects. Instead, the audio drops immediately to a reorder tone and the line is marked out of service if it does not go on hook within a few seconds. Going on-hook for a while (more than a few seconds) will return the line to in-service status without manual intervention - a good thing, since our switchroom is unattended from early evening on. As you might guess, this lack of supervision is a major pain for answering machines, modems, and such, requiring that they sense the reorder tone and disconnect. Luckily, the reorder tone (a high/low warble) is not sensed as carrier for very long by most modems, although many spew incredible amounts of garbage on the screen when this happens. It's even more annoying in that calls to out-of-service lines are forwarded to the attendant's position, which if unmanned after hours, either gives an inappropriate recording or just rings no answer. I am told that the number of analog lines with loop supervision is also quite limited - apparently the interface cards with loop supervision can only support a few lines each, whereas they get several lines per card for the non-supervised lines. - Brian