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From: AWalker@RED.RUTGERS.EDU (*Hobbit*)
Newsgroups: mod.telecom
Subject: active-line indicator
Message-ID: <12153191012.61.AWALKER@RED.RUTGERS.EDU>
Date: Tue, 22-Oct-85 13:52:07 EDT
Article-I.D.: RED.12153191012.61.AWALKER
Posted: Tue Oct 22 13:52:07 1985
Date-Received: Wed, 23-Oct-85 13:24:13 EDT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The ARPA Internet
Lines: 19
Approved: telecom@ucb-vax.arpa

Line ------------------------------------------------> to devices

                100 ohms
           +--/\/\/\/\/\/--+
           |               |
Line ------+------|<|------+-------------------------> to devices
           |               |
           +------|>|------+
                  LED

The thing in the middle is a regular diode pointing the other way.  If you
want to get fancy, you can use a green LED pointing one way and a red one
pointing the other [in place of the regular one], which will indicate line
polarity.  The 100 ohm resistor passes some of the line current and protects
the LEDs.  This will give you an almost indiscernible current drop at the 
phone end...

_H*
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