Article View: sci.electronics
Article #4922Re: How Do I Make a Phone In-Use Light?
From: Terri Barber
Date: Mon, 02 Jul 1990 21:30
Date: Mon, 02 Jul 1990 21:30
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In article <4633@milton.u.washington.edu> wiml@milton.u.washington.edu (William Lewis) writes:
>In article <904@eplunix.UUCP> raoul@eplunix.UUCP (Nico Garcia) writes:
>>In article <1558@yenta.alb.nm.us>, dt@yenta.alb.nm.us (David B. Thomas) writes:
>>> Another neat phone circuit (VERY simple) uses an scr, a couple of resistors
>>> and a button. If you wish to switch phones, you hold in the button (gating
>>> the scr), then hang up. The scr maintains loop current. An led could be
>>
>>Ummm, can you post this one? Enough of us do occasional phone hacking that
>>I'd like one as well.
>
>
> I second that. It would be extremely useful around here ...
Okay, let's see if I can remember how to do it (I didn't post the original,
I just want to stick my $.02 in....
Please excuse the ascii graphics....
-------------------+------+----
| |
| /
| / momentary switch
| |
| /
| \ 1200 Ohm
| /
-----____|
/ \
/___\ SCR
|
/
\ 600 Ohm
/
| ^^
----- //
/ \ //
/___\ LED
|
|
-------------------+---------
Technical Details
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Path: arc1-ca.pugleaf.net!utzoo!attcan!uunet!tut.cis.ohio-state.edu!ucsd!sdcc6!beowulf!barber From: barber@beowulf.ucsd.edu (Terri Barber) Newsgroups: sci.electronics Subject: Re: How Do I Make a Phone In-Use Light? Message-ID: <11707@sdcc6.ucsd.edu> Date: 2 Jul 90 21:30:58 GMT References: <1558@yenta.alb.nm.us> <904@eplunix.UUCP> <4633@milton.u.washington.edu> Sender: news@sdcc6.ucsd.edu Organization: CSE Dept., U. C. San Diego Lines: 40