Abstract: A meter interface unit for use in a one way automatic meter reading system comprises first means for frequently transmitting a short burst transmission suitable for reception by a hand held or mobile receiver, and second means for transmitting narrow band data messages suitable for reception by a fixed network first tier receiving station. The receiver at the first tier receiving station has means for suppressing the short transmissions to prevent interference with the slow busts from the second transmitting means. Repeated packet collisions between the short bursts are avoided by randomly varying the time period between the short bursts.

Abstract: A meter interface unit for use in a one way automatic meter reading system comprises first means for frequently transmitting a short burst transmission suitable for reception by a hand held or mobile receiver, and second means for transmitting narrow band data messages suitable for reception by a fixed network first tier receiving station. The receiver at the first tier receiving station has means for suppressing the short transmissions to prevent interference with the slow busts from the second transmitting means. Repeated packet collisions between the short bursts are avoided by randomly varying the time period between the short bursts.

Abstract: A fixed network AMR system that has a range from the meter (4) to the node (6) of up to 5 km uses a common reference source (2) for the frequency reference of the meter transmitter (12) and the system receiver (18). By using a publicly available reference frequency the necessary frequency stability can be obtained in order to provide a signal to noise bandwidth of the order of 32 Hz.

Abstract: A low power density radio system is provided using a simple FSK transmitter arranged to transmit very short bursts to a receiver at predetermined frequent intervals. Such a system can be used between a meter transponder and a reader in an AMR system to eliminate the need for a receiver in the transponder and still achieve extended battery life. The problems of detecting and demodulating the short burst are overcome by using a sample and hold circuit that detects a preamble signal of reversals to indicate the presence of the burst. The sample and hold circuit also provides the reference value to correct for the DC pedestal voltage that arises as a function of the transmitter and receiver frequency errors. The data signal that follows the preamble signal can then be detected, and is followed by a verifying signal as part of the signal burst. The burst signal is repeated at predetermined intervals and is preferably only {fraction (1/4000)} or less than the signal time interval.

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.