Props to Vitali Virulaine at http://www.vital.pri.ee/PSTN/ for coming up with, and sam for inspiring me to show him up, I hope you get into the maxim party!!!
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Signing UpStep 1: Parts needed
-an RJ11 Plug (buy a cheap phone cord and cut off one end)
-2 100OHM resistors
-500OHM variable resistor
-2 3.3uF capacitors
-9V adapter, or USB plug, or use the one currently in your phone.








































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Thanks
please leave me a note if you've found something
the one on http://www.vital.pri.ee/PSTN/ is the same one used here
Looking at the way that the circuit uses the two USB ports, it's so as to get a total of 10V instead of 5V for the circuit (which, with the battery, is 9V). I think you could use a single USB port for power if you were willing to build a circuit to up the 5V to 9V... but you might end up going over the 100mA limit that a USB port will give to a device. It's a bit of an ugly hack either way - I'd pull 12V from a spare Molex connector and fiddle with the pot to control the gain.
Last night, when I saw this, I thought of a really neat way to use this circuit - marry it up to one of these cheap USB audio adaptors...
http://tinyurl.com/mh762
...and hook it up to an internal USB header - taking the power from a spare Molex connector, as mentioned above - and wire up a standard phone jack to a blanking plate - maybe even one stolen from an old modem =)
That would be fab stuff.
should be custom.