Go here and you can get the Order Number
for the service manual: Call 1-800-THE-SHAC
http://support.radioshack.com/suppor...oc21/21316.htm

Most scanners pack the Disc/Squelch/Mute/Scan Control all
on the same chip. By looking at the parts list, it looks as if
our scanner uses a TD62501P for this, but without the service
manual, I cant tell. A google search for this part didn't find any
free datasheets. Good luck.