Path: utzoo!attcan!utgpu!news-server.csri.toronto.edu!rutgers!apple!bionet!hayes.fai.alaska.edu!accuvax.nwu.edu!nucsrl!telecom-request From: vision!davel@relay.eu.net (Dave Lockwood) Newsgroups: comp.dcom.telecom Subject: Re: Leaving Brief Messages With Free Collect Calls Message-ID: <12126@accuvax.nwu.edu> Date: 13 Sep 90 14:15:28 GMT Sender: news@accuvax.nwu.edu Reply-To: Dave Lockwood Organization: VisionWare Ltd., Leeds, UK Lines: 22 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 643, Message 7 of 8 In various articles, various people write: About answering the phone before it rang... In the UK, before the advent of the digital switch, all the electromechanical (Strowger and Crossbar) switches generated ring current and tone by means of a rotating motor with a commutator pair. Examining this device showed that the ring tone (to caller) and the ring current (to callee) would be exactly "out of phase", ie the ring current was sent in the gaps between the ring tones. Incidentally, the same motor/commutator used to produce the busy signal too. Dave Lockwood ...!uunet!mcsun!ukc!vision!davel davel@vision.uucp Technical Consultant ...!uunet!bulus3!bungia!vware!davel davel@vware.MN.ORG VisionWare Ltd, G4CLI@GB7YHF.194.GBR.EU dave@g4cli.ampr.org 57 Cardigan Lane, D.LOCKWOOD@ICLX davel@vision.co.uk Leeds, LS4 2LE, +44-532-788858 +44-831-494088 United Kingdom +44-532-304676 "Hey, You!"