Article View: sci.electronics
Article #9656Re: RS-232 powered modems
From: Michael A. Covington
Date: Sun, 20 Jan 1991 23:28
Date: Sun, 20 Jan 1991 23:28
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In article <19983@hydra.gatech.EDU> jgb@prism.gatech.EDU (James G. Baker) writes: >I've seen small 2400 baud modems that *only* have COM and phone connections. >How do these pull power from the telephone or computer? I need to make a >box with similar needs (a few LS parts) and of course they need a +5 power >supply. Is there a +5V line on RS-232C and is it standard with DB25 and DB9 >connectors? Or is there a +12,etc that I could feed into a voltage regulator? > No, there are no power lines. What you can do is use switching diodes to automatically give you a path to the most positive pin(s) and draw just a _little_ power from them. It has to be micropower (on the order of 1 mA).
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arc1-ca.pugleaf.net!utzoo!censor!geac!torsqnt!lethe!yunexus!ists!helios.physics.utoronto.ca!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!samsung!zaphod.mps.ohio-state.edu!wuarchive!emory!athena.cs.uga.edu!mcovingtReferences:
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Path: arc1-ca.pugleaf.net!utzoo!censor!geac!torsqnt!lethe!yunexus!ists!helios.physics.utoronto.ca!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!samsung!zaphod.mps.ohio-state.edu!wuarchive!emory!athena.cs.uga.edu!mcovingt From: mcovingt@athena.cs.uga.edu (Michael A. Covington) Newsgroups: sci.electronics Subject: Re: RS-232 powered modems Message-ID: <1991Jan20.232819.23502@athena.cs.uga.edu> Date: 20 Jan 91 23:28:19 GMT References: <19983@hydra.gatech.EDU> Organization: University of Georgia, Athens Lines: 11