Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!world!jon_sree From: jon_sree@world.std.com (Jon Sreekanth) Newsgroups: sci.electronics Subject: Re: phone line power Message-ID: Date: 11 Feb 91 16:25:50 GMT References: <13284@life.ai.mit.edu> Sender: jon_sree@world.std.com (Jon Sreekanth) Organization: The World Lines: 28 In-Reply-To: campbell@.ai.mit.edu's message of 10 Feb 91 05:30:23 GMT In article <13284@life.ai.mit.edu> campbell@.ai.mit.edu writes: charge pumped device (DC-DC charge pumped devices, there are lots of these listed at +/-48 volts in the catalogs I have). I'm wondering if you intend to draw power from the telephone line when it's on-hook (meaning, not being used). The on-hook DC resistance of any device you connect to the telephone line should be more than 5 Meg ohms. 5M gives you a ringer equivalence number of 5, which is the maximum permissible, meaning you cannot have any other device on the line. (REN measures how much DC and AC load you impose upon the telephone line. Common phones have a REN of 1.0. FCC limits you to a maximum of 5.0 when you add up all the devices connected to that line. ) 1. Will this work? I'm not entirely sure so the only way to tell is to experiment. I've seen ads for laptop modems that are line powered, so it's doable. After you've picked up the line, you can draw a fair amount of DC power from the line : usually there's 20 - 25 mA at about 8V. Regards, / Jon Sreekanth Assabet Valley Microsystems Fax and PC products 346 Lincoln St #722, Marlboro, MA 01752 508-562-0722 jon_sree@world.std.com