🚀 go-pugleaf

In article <5847@brspyr1.BRS.Com> miket@brspyr1.BRS.Com (Mike Trout) writes:
>
>The chip used is a TI TX8835 N 96856.  It is connected to a 9-dipswitch unit
>with 3 positions per switch.  I'm assuming that this allows certain pins on the
>chip to be placed high, low, or neutral.  As there are thousands of possible
>combinations, I have no way of finding out what the possible frequencies for
>this chip may be.

This is admittedly just a guess, but is based on knowledge of my own
garage-door transmitter.  The dipswitches probably don't alter the
frequency at all, but control some sort of code modulated onto the
carrier.  This is supposed to provide greater security and prevent a
would-be-thief from simply driving up to your house and blasting
selected frequencies at your garage until the door opens, or simply
carrying a number of common door-opener transmitters and trying them
until one works (don't laugh, it happens).  The number of possible
codes in my case is 2^10 (1024), since there are 10 dipswitches.

The frequency is most likely determined by a crystal oscillator.
There's probably a tuning coil with a powdered-iron slug for tweaking
it, although not all designs have this.  Some only have fixed
inductors and a small trimmer capacitor for matching with the printed
circuit loop "antenna".


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