On 07/17/2012 06:12 PM, Pat wrote:
On Tue, 17 Jul 2012 13:38:45 -0700, "Guv Bob"
wrote:

[snip]

If it is *really old*, they didn't use codes. All the remotes were
pretty much on the same RF frequency (really realy old was 27 MHz,
just really old on 300MHz). They modulated the carrier with one of a
dozen or so audio tones to avoid interference with your neighbors.


I had one of those until I had to replace it 3 years ago (defective
opener wouldn't reverse when hitting something o tore up the door).
Apparently, you would change it by moving the core inside the coil.

--
Mark Lloyd
http://notstupid.us

"Eskimo: If I did not know about God and sin, would I go to hell?
Priest: No, not if you didn't know. Eskimo: Then why did you tell me?"