Found at: 0x1bi.net:70/textfiles/file?hamradio/fm_monitor.txt

                         MAKING AN FM MONITORING DEVICE
                         CHEAP, SMALL, AND INTERESTING!
                              Written by: T.M.M.
      Well, there are many files on "bugs", but most of them rely on
complicated equipment.  The bug described in this file is simple to install,
and to use.  It uses FM freqencies, tunable on your radio, and only draws power
from the batteries when the phone is of the hook.
           A "Mr. Microphone" type FM wireless mike w/ batteries
                    (Radio Shack # 60-2109, 6 bucks I think)
           The Phone to Be Monitored
             (Preferably a standard desk or wall phone, others are more
             complicated to do)
      The first step is to tune the mic to the desired frequency. It is best to
tune to the ends of the band (somewhere around 88 or 108 mhz) When it is tuned,
the wires on the mic as close to the mic element as you can (to make use of the
most wire). Then take the PC board assembly out of the case.
      Then remove the cover of the phone exposing the wires, ringer etc. What
you need to do is trace the the wires coming in from the handset. If you don't
know what they are, unscrew the cover on the earpiece, and lift up speaker.
Look at the wires, on most phones, they are white and an olive green. Find
block near the center of the phone. You then connect the mic wires that you cut
to the two screws that have the speaker cords hooked up to them.
      You then have to trace the switchhook wires to the block. You connect one
conversation is sent to your radio or walkman!
Have PHUN, and don't get caught... I think it's legal if one of the people in
the conversation knows about the monitoring, but who gives a shit!