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Article #4854Re: How Do I Make a Phone In-Use Light?
From: Marvin Jones
Date: Wed, 27 Jun 1990 17:29
Date: Wed, 27 Jun 1990 17:29
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Perhaps one solution here would be to use a Low Voltage Detector, such as the
Seiko 8054 series or the Motorola MC34164. These are typically used to provide
an open drain pulldown at the output (for driving processor reset lines)
when the input voltage "browns out" below 4.7 volts or so. With a divider
network on the input, this could be adapted to 10 volts or whatever
threshold you desire. The open drain output could pull down an LED/limit
resistor to indicate "in-use". The system should reset itself automatically
when the voltage increases again. One would need to provide a zener clamp or
resistive current limiting to protect the device from up to 60 volts of open
circuit "on-hook" voltages.
Hmmm. Just might work.
--
=== Marvin Jones === Optilink Corp. === Petaluma, CA === 707.795.9444 X206 ===
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Path: arc1-ca.pugleaf.net!utzoo!utgpu!news-server.csri.toronto.edu!mailrus!cs.utexas.edu!uunet!optilink!jones From: jones@optilink.UUCP (Marvin Jones) Newsgroups: sci.electronics Subject: Re: How Do I Make a Phone In-Use Light? Summary: How about Low Voltage Detectors? Message-ID: <3883@optilink.UUCP> Date: 27 Jun 90 17:29:34 GMT References: <2204@sauron.Columbia.NCR.COM> <5349@mmsac.UUCP> Distribution: usa Organization: Optilink Corporation, Petaluma, CA Lines: 18