=20
> Interestingly, they interrogate and send power at 125 kHz but
> get pressure back at 433 MHz using (they say) frequency offset
> of signal as pressure indication. Presumably the actual modulation
> is somewhat more sophisticated than that implies

It's possibly to make it compatible with established monitoring
systems. Usually, AIUI, the pressure sensor is rim-mounted (not in
the tyre) around or part of the valve and battery-powered, data being
sent to the ECU or whatever via a local 433MHz unit. The 125kHz
excitation signal would take the place of the battery (as well as being
the obvious through-rubber comms), and the data is sent on from the
RFID receiver with an OTS 433MHz transmitter

Joe
--=20
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