Comments on: The Amateur Electrician: Build a Telephone http://blog.modernmechanix.com/2007/10/26/the-amateur-electrician-build-a-telephone/ Yesterday's tomorrow, today. Sun, 22 Nov 2009 18:36:33 -0800 http://wordpress.org/?v=2.8.4 hourly 1 By: Dag S http://blog.modernmechanix.com/2007/10/26/the-amateur-electrician-build-a-telephone/comment-page-1/#comment-1063077 Dag S Thu, 27 Nov 2008 18:37:04 +0000 http://blog.modernmechanix.com/2007/10/26/the-amateur-electrician-build-a-telephone/#comment-1063077 The coil has 2 purposes, 1 as an impedance transformer, low ohms at tramsitter, high at receiver. 2: What probably was on the next page or number was how to make a call signal. Making the buzzer work with an high note, the receivers will howl. This solution has been used by e.g. british armed forces, and on some old telephonesystems. It works well, but you may imagine how it is if somone send that sound ino your ear when having the receiver into your ear. The coil has 2 purposes, 1 as an impedance transformer, low ohms at tramsitter, high at receiver.

2: What probably was on the next page or number was how to make a call signal.
Making the buzzer work with an high note, the receivers will howl.

This solution has been used by e.g. british armed forces, and on some old telephonesystems.

It works well, but you may imagine how it is if somone send that sound ino your ear when having the receiver into your ear.

]]> By: Jamie http://blog.modernmechanix.com/2007/10/26/the-amateur-electrician-build-a-telephone/comment-page-1/#comment-1062292 Jamie Sat, 01 Nov 2008 02:04:11 +0000 http://blog.modernmechanix.com/2007/10/26/the-amateur-electrician-build-a-telephone/#comment-1062292 The coil is used to match the low impedance of the transmitter to the higher impedance of the line. The coil is used to match the low impedance of the transmitter to the higher impedance of the line.

]]> By: George T http://blog.modernmechanix.com/2007/10/26/the-amateur-electrician-build-a-telephone/comment-page-1/#comment-1046997 George T Sun, 17 Feb 2008 02:26:45 +0000 http://blog.modernmechanix.com/2007/10/26/the-amateur-electrician-build-a-telephone/#comment-1046997 Yes, the interrupter is either bypassed or screwed down tight so it won't buzz, then the coil is used as an audio transformer. A big oversight in that design though, is there's no ringing circuit. I guess you could either set up talking times, or send your friend a letter or telegram when you want to talk... (a bit of possibly apocryphal telephone trivia is when Mr. Bell patented the telephone, he thought the main use for it would be to notify people there was a telegram coming) Yes, the interrupter is either bypassed or screwed down tight so it won’t buzz, then the coil is used as an audio transformer. A big oversight in that design though, is there’s no ringing circuit. I guess you could either set up talking times, or send your friend a letter or telegram when you want to talk… (a bit of possibly apocryphal telephone trivia is when Mr. Bell patented the telephone, he thought the main use for it would be to notify people there was a telegram coming)

]]> By: Orv http://blog.modernmechanix.com/2007/10/26/the-amateur-electrician-build-a-telephone/comment-page-1/#comment-649789 Orv Sun, 28 Oct 2007 08:02:34 +0000 http://blog.modernmechanix.com/2007/10/26/the-amateur-electrician-build-a-telephone/#comment-649789 It looks like they're using it to step up the voltage of the audio signal. By reducing the current, that reduces the amount lost in the long run of wire between the phones (and in the ground return.) It looks like they’re using it to step up the voltage of the audio signal. By reducing the current, that reduces the amount lost in the long run of wire between the phones (and in the ground return.)

]]> By: MC http://blog.modernmechanix.com/2007/10/26/the-amateur-electrician-build-a-telephone/comment-page-1/#comment-646050 MC Sat, 27 Oct 2007 04:50:58 +0000 http://blog.modernmechanix.com/2007/10/26/the-amateur-electrician-build-a-telephone/#comment-646050 Curious circuit. At first I thought that "Ford spark coil" meant the whole buzzing high-voltage device used by a Model T, which would produce a terrible racket. Apparently not. I now think they mean just the coil, and they're using it as an audio-frequency transformer. Any insights, anyone? Curious circuit. At first I thought that “Ford spark coil” meant the whole buzzing high-voltage device used by a Model T, which would produce a terrible racket. Apparently not. I now think they mean just the coil, and they’re using it as an audio-frequency transformer. Any insights, anyone?

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