The power comes from a transformer which is wired to the first and third
legs of the receiver, legs one and two are then wired to the push-button's
terminal. Any do-it-yourselfer can add on a radio set following the simple
to follow directions included in the box.
Here's a diagram:
http://www.garage-door-hardware.com/delta3.html

Another receiver that can be used is LiftMaster's 635LM Universal plug-in
receiver http://www.garage-door-parts.com/cha...ter-radio.html
They could just plug it in and hard wire it directly to any garage door
opener strip. That along with a 971LM transmitter also found on that page
and the problem is solved.

Just because the receiver circuit is on the blink doesn't necessarily mean
that the whole machine will be in the crapper soon. Shame on you for even
suggesting that "DoorDoc?"