Path: utzoo!attcan!uunet!wuarchive!brutus.cs.uiuc.edu!lll-winken!netsys!vector!telecom-gateway From: sklar@ihlpl.att.com (Robert S Sklar) Newsgroups: comp.dcom.telecom Subject: Re: Unusual Warning Notice on Phones Message-ID: Date: 23 Aug 89 19:07:42 GMT Sender: news@vector.Dallas.TX.US Organization: AT&T Bell Laboratories Lines: 34 Approved: telecom-request@vector.dallas.tx.us X-Submissions-To: telecom@eecs.nwu.edu X-Administrivia-To: telecom-request@vector.dallas.tx.us X-TELECOM-Digest: volume 9, issue 320, message 6 of 10 In article , judice@kyoa.enet.dec.com (Lou Judice 15-Aug-1989 0916) writes: > While moving offices recently, we noticed the following odd label on the > bottom of AT&T straight sets (normal single line phones): > > WARNING > > USE FOR BUSINESS SYSTEMS ONLY OR YOU > RISK AN ELECTRICAL SHORT CIRCUIT. > > > The phones are on a Dimension PBX. I'm sure I've put consumer phone stuff > on a Dimension without frying it, so I'm curious about this. (Note, I > could understand if this was a digital phone or a MET-set type phone). > > /ljj The reason for the warning is probably for the sub-case where someone attempts to plug this phone into an RJ14 *TWO-LINE* jack. A business analog phone, probably a 2500M, is wired differently than its residential equivalent, a 2500D. The business phone uses the yellow-black pair for A-A1 supervision (the hook-switch short-circuits the pair so that the PBX|KSU knows that the line was picked-up and can light the appropriate lights on multi-line phones). On a 2500D this hookswitch pole is used for other purposes. Therefore, if you install a 2500M or equivalent in a two-line residential installation without opening the yellow-black connection to the hookswitch, you will short-out the second line every time you pick up this phone. Robert Sklar (Lachman Associates, Inc @) AT&T Bell Laboratories Naperville, IL