I have two AT&T model 1475 cordless phones. (I know they are quite
old, but I like the feel of the phone even though it is a 2.4GHZ phone.)
I acquired the second one for a few dollars primarily for parts if the
first one crapped out. Both of the units work just fine in all respects.

Since they are the same model and the phone from one does NOT work on
the other base unit, I assume there is a different frequency that each
is running at. I opened up one unit and I did notice a crystal tacked
on the back of the PWB that I assume is unique for each pair.

My question: Just out of curiosity, what do the manufacturers do to
make their same model cordless phone communicate with only the base it
belongs? My guess is they change something simple like the crystal on
both the base and handset so that there is a distinction between units.
Anyone know?? Thanks.