Without even looking at the reference, this sounds wrong. The IC may exist but methinks most Telco's would not let you use it. Assuming this is a switching regulator with 100% efficiency this would require 5ma at 50 volts or an equivalent load resistance of 50/.005 = 10k. This looks like a VERY bad line to any sort of test equipment and would upset Telcos no end. Also, I suspect that this is getting close to the real line seize current in some circumstances and there are circuits which are designed to trip to a high resistance loop and trip eg ringing prior to answering (operator intervention circuitry) so this would run foul of this. Realistically, anything over 1 megohm loop would probably be OK in practice (100K too but test equipment should flag it as a pending fault). 1meg gives you 50 uA or 2500 uwatt. 100% efficiency gives you 500uA at 5 volts. Good enough to run a micro and charge a battery. 100K gives you 10 times as much. Russell McMahon. ========================== -----Original Message----- From: Art Allen, KY1K To: PICLIST@MITVMA.MIT.EDU Date: Saturday, 11 September 1999 15:08 Subject: Re: line powered device >Yes, the circuit and explanation is shown @ >http://209.1.238.246/1st_pages/A1208.htm > >The chip is a max638 and it looks like 50 ma @ 5v regulated can be drawn >from the line when the phone is not in use. > >Regards, > >Art > > > > >At 06:47 PM 09/10/1999 +0200, you wrote: >>Art, >> >>I visited the site but had no luck in finding the part. >> >>Do you have the chip number at hand ? >> >>Thank you >> >>Duilio >> >> >>At 10.26 10/09/99 -0400, you wrote: >>>At 02:58 PM 09/10/1999 +0200, you wrote: >>>>I'd like to know how much current can be legally drawn from the CO line >by a >>>>line-powered device. >>>> >>>>Do you know of any line-powered circuit avaiable in the net ? >>>> >>>>Thank you >>>> >>>>Duilio Foschi >>>> >>>> >>> >>>Maxim has an ap note on this and a special chip for extracting power. >>> >>>It's at www.maxim-ic.com >>> >>>Look for the ap note first and get the chip number from that .pdf document. >>> >>>Art >>> >> >> >