From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262852AbULRH7K (ORCPT ); Sat, 18 Dec 2004 02:59:10 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262853AbULRH7K (ORCPT ); Sat, 18 Dec 2004 02:59:10 -0500 Received: from wasp.net.au ([203.190.192.17]:20417 "EHLO wasp.net.au") by vger.kernel.org with ESMTP id S262852AbULRH7G (ORCPT ); Sat, 18 Dec 2004 02:59:06 -0500 Message-ID: <41C3E34D.4090203@wasp.net.au> Date: Sat, 18 Dec 2004 11:59:09 +0400 From: Brad Campbell User-Agent: Mozilla Thunderbird 1.0RC1 (X11/20041201) X-Accept-Language: en-us, en MIME-Version: 1.0 To: manu@kromtek.com CC: David Lawyer , Pavel Machek , Park Lee , linux-kernel@vger.kernel.org Subject: Re: Issue on connect 2 modems with a single phone line References: <20041215184206.43601.qmail@web51505.mail.yahoo.com> <20041216085828.GG1189@lafn.org> <41C3D5AD.7090507@wasp.net.au> <200412181145.59211.manu@kromtek.com> In-Reply-To: <200412181145.59211.manu@kromtek.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Manu Abraham wrote: > On Sat December 18 2004 11:01 am, Brad Campbell wrote: >>I have used analogue modems back to back for years and have *never* come >>across a modem that sourced anything other than it's ringing signal (via an >>opto) from the phone line. Every single modem I have here will talk to the >>others over a straight telephone cable. > > What about power ? The opto-coupler will not work without power. > If you read what I wrote you will note the opto-coupler is used for ring detection only and then only triggers when it sees an AC ring pulse. You don't need ring detection to run modems back to back and therefore it's not a problem. As for the Capacitor and Transformer, you are correct. I merely mis-communicated my message. Point is the same, you can connect 90% of Analogue modems back to back with only a bit of wire and they will talk. (I say 90% as I'm sure there is one out there somewhere that uses the phone line voltage for something but I have *never* seen one). Remember that off-hook phone voltages can get down to around 3v while on hook you may have 50v. Don't theorize about it, try it. -- Brad /"\ Save the Forests \ / ASCII RIBBON CAMPAIGN Burn a Greenie. X AGAINST HTML MAIL / \