Abstract: A remote meter reading system uses transponders adapted to transmit a spread spectrum signal which is generated by frequency modulating data with a carrier signal. The resulting output signal is then spread by phase modulating with a pseudo-random code signal before transmission with the carrier suppressed. At the receiver, the original suppressed carrier is regenerated by squaring a first IF signal and then applying the output signal to a narrow band receiver from which the data can be recovered with a conventional FM discriminator.

Abstract: A sensor for counting rotations of a Ferraris disk in an electricity meter. The disk has a light reflecting surface carrying a broad stripe marking. The sensor comprises two IR LEDs spaced at either side of an intermediate photo-transistor adapted to receive light reflected from the disk from both LEDs. The LEDs are spaced in the direction of rotation by at least the width of the stripe. As the stripe passes across the detector, the output signal generated has characteristic shoulders on its falling and rising edges. By detecting this characteristic pattern and checking that the LEDs which contribute to the signal at the shoulder point are in the correct sequence for the normal direction of rotation, it is possible to detect false counts caused by jitter, tampering or changes in ambient light level.