Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!accuvax.nwu.edu!nucsrl!telecom-request From: John Higdon Newsgroups: comp.dcom.telecom Subject: Re: Loop Start vs Ground Start, a User Intro Message-ID: <6111@accuvax.nwu.edu> Date: 6 Apr 90 04:55:44 GMT Sender: news@accuvax.nwu.edu Reply-To: John Higdon Organization: TELECOM Digest Lines: 23 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 235, Message 7 of 11 George Horwath writes: > 2) Depending on how bad glare is/ground start trunk availability/costs/etc., > loop start trunks can be marked as one-way incoming or one-way > outgoing but now more trunks are needed. This feature also depends on > the brand of PBX. In the real world of modern CO switches (1ESS or newer) glare is a negligible problem. Unlike SXS and crossbar, electronic/digital switches apply ring current simultaneously with the connection to the called party. Once any PBX sees that ring, the trunk is instantly taken out of the pool for outside calls. Therefore, even systems with loop start trunks need not segregate the available lines for incoming vs outgoing. (It may not seem as though ring is applied instantly, since all electronic/digital switches will at least occasionally provide ringback which is out of phase with the actual ring voltage cadence applied to the called line.) John Higdon | P. O. Box 7648 | +1 408 723 1395 john@bovine.ati.com | San Jose, CA 95150 | M o o !