OnFebruary 18, Jon Elson wrote:
>> A question concerning the car remotes; door lock, headlights, etc.
>> Each car/handset must be a matched pair, regarding the ID
>> and security codes. Obviously only one car in the parking
>> lot ought to respond.
>> Are the ID codes determined by each manufacturer, as
>> they choose? Or is there an intern'l body which allocates
>> them, such that each is guaranteed unique, just as
>> every telephone has a unique number?
>
> Well, they have a chip that is programmed at the factory, probably with a
> sequentially-incremented number. The car is then trained to accept several
> key's serial numbers. The all-in-one keys/fobs have two chips, one operated
> by pushbutton with a coin cell for door unlock, and one RF-powered by the
> engine computer through a coil near the ignition lock, for immobilizer.
So, each manuf'r has its own allocation of ID numbers. And, presumably, its own
RF format. Are there FCC regs on that?
> So, in theory, there should be no two cars anywhere that respond to the same
> code.
Well, no. There's no intern'l body allocating the codes, so in theory, there
could be duplication.
Whereas, in the phone network, you dial a number, it's guaranteed to ring exactly
one target device.
--
Rich