Chuck,
Earliest Garage door openers used discrete transistor designs, but a
National Semiconductor
chip seemed very popular for quite a long time. (Look for a 14pin dip package
with NS...someting
on it. ) Nowdays people often use the "Industrial, Scientific and Medical"
(ISM) bands at 300MHz
or 900MHz. Search for and read the "lynx" website for good overview of US
domestic and
international product use. Typically now, for low cost aplications they seem to
use SAW stabilised
oscillators, like in the Lynx products.
Tim Hughes
--- Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx> wrote:
>
> As to the origins of the electronics in these cheap Chinese radio slaves
> I suspect that they are derived from garage door openers. The size of
> the transmitter PC board and the use of a 12 volt 23A battery looks like
> a near duplicate of my circa 1996 Lift-Master garage door opener.
>
> Chuck Norcutt
>
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