The Solartron Electronic Group Limited

Sangamo Weston, Inc.

Howard A Dorey

Robert John Cooke

Michael I Spooner

Anthony J Ley

Eric Metcalf

Geoffrey Arthur Luckhurst

Michael J Skinner

Edward A Martin

Jack Woollven

A receiver, for receiving a signal comprising a carrier signal modulated with a digital signal, comprises a circuit for demodulating the received signal to produce an output signal which contains the digital signal. Because of repeated filtering, the digital signal is typically in the form of an approximately sinusoidal signal, which has a component whose frequency is equal to half the basic bit rate of the digital signal: because of noise, this component is subject to considerable timing jitter. To overcome this, the output signal is digitized and applied to a digital correlator, where it is correlated with a reference signal whose frequency is also equal to half the basic bit rate of the digital signal. The reference signal is preferably derived from a phase-locked loop locked to the carrier frequency. The correlator, which is constituted by a microprocessor, determines the instants of time which most nearly coincide with the mean-level crossing points of said component (which instants correspond to transitions between one bit of the digital signal and the next), and also determines successive bit values on the basis of the coincidence determination. The receiver can be used to receive mains-borne signals, i.e. signals transmitted over an electrical power supply network, or radio broadcast signals.

Method and apparatus for receiving carrier-borne digital signals

An electricity meter for metering the amount of electrical energy supplied by a power supplier to a power consumer is provided with fraud detection means for detecting the presence of an external shunt which has been connected to by-pass its internal current sensing means. The detection means, which comprises a differential current sensor for sensing the difference between the respective currents flowing to and from the consumer via the meter and a multiplier for multiplying this current difference by a signal derived from the supply voltage, is arranged to operate a circuit breaker, and/or to compensate the energy measurement of the meter, and/or to provide a warning to the supplier. The differential current sensor also senses when current is being taken between the live wire and earth on the consumer's side of the meter.

Electricity meters

A transmission system, for transmitting signals over an electrical power distribution circuit, comprises a transmitter arranged to produce at least two carrier signals of different frequency and to modulate each of them with the same digital signal. The respective frequencies of the carrier signals are derived by frequency division from a common master oscillator, and are thus phase-coherent. The system includes a receiver for receiving the signals, comprising a respective input circuit for each modulated carrier, the input circuits each being tuned to the frequency of their respective carrier signal. A plurality of oscillator signals of different frequencies, derived from a variable frequency oscillator, are used to beat the received carrier signals to respective signals at a common frequency, which signals are summed. The summed signal at the common frequency is applied to one input of a phase detector, whose other input is connected to receive another oscillator signal, also at the common frequency, from the variable frequency oscillator. The output signal from the phase detector is applied to the variable frequency oscillator to lock its frequency to those of all the carriers and therefore to that of the master oscillator in the transmitter. The digital signal is derived from the output of the phase detector by digital correlation techniques.

Transmission systems for transmitting signals over power distribution

A radio-controlled device for use in a power distribution circuit, typically for tariff-switching, load-shedding or off-peak load-switching purposes, includes a radio receiver having an aerial circuit which includes a ferrite annulus. The device is typically mounted in an electricity meter connected in the power distribution circuit, with the ferrite annulus surrounding one or more wires of the distribution circuit down-circuit of the meter. The wire or wires surrounded by the ferrite annulus, which typically extend all over the house or other building in which the meter and the device are installed, therefore serve as an aerial for the radio receiver in the device, thus alleviating the problems which can arise when the device is mounted in a location where radio reception is poor.

Radio-controlled devices for use in power distribution circuits

A single patch on an integrated circuit is arranged to patch any one of four different logical states into the circuit, according to whether the pin is grounded, floating, coupled to a supply rail via a resistor, or coupled to the supply rail directly. In one embodiment, the voltage thresholds of three transistors are arranged so that they switch on successively in response to successively higher voltages on the patch pin, thereby controlling the binary logic signals at each of two output points in the circuit; in the other embodiment, multi-emitter transistors are arranged with differing current thresholds to achieve the same result.

Multi function patch pin circuit

An interface circuit for use in a data transmission system has a first port for connection to a 16 wire data highway of the type proposed by the I.E.C. (International Electrochemical Commission) for the interconnection of instruments, and a second port capable of being connected to an eight-wire or two-wire data link. The interface circuit includes an encoding circuit operative to encode at least some commands applied to the first port, and an enabling circuit for selectively enabling data applied to the data terminals of the first port and the encoded commands to pass to the second port. The interface circuit also includes status circuits for establishing statuses of the circuit in accordance with commands supplied thereto, including a status indicating that the interface has been addressed, and a circuit responsive to the absence of this 'addressed' status to disable the enabling circuit, so as to prevent at least some of the encoded commands and the data received at the data terminals of the first port from being passed to the second port.

Interfaces for connecting coded and non-coded data transmission systems

An interface circuit for use in a data transmission system is designed to be used not only between a highway and a device but also to link highways and can be commanded to enter a status in which commands sent to it on one highway are modified and sent out as commands on a second highway so that a controller device on the one highway can control devices not only on that highway but also on the second highway, with extension, if desired, to a third highway or beyond. To achieve this, the interface circuit has two ports each for connection to a respective one of two substantially identical highways, and status control means responsive to signals received at either port to establish different statuses of the interface. For inter-highway communication, the status control means is responsive to a command signal of particular form at either port to produce a modified command signal at the other port.

Interface circuit for communicating between two data highways

In a multi-device data transmission system with source and acceptor devices linked by a data highway and handshake lines, provision is made for automatically adjusting the delay of the handshake cycle to suit the highway length and other determinative factors. This is achieved in that the acceptors do not accept data until told so to do via one handshake line, whereas the source is only allowed to issue this command when it has been told via another handshake line that all acceptors have seen the data. The system determines its own delay in this way and automatically adapts the delay to whatever length of highway is employed, whether a fraction of a meter in a circuit board or several tens of meters in inter-rack wiring.

Data transfer control apparatus

Electronic analogue to digital converters of the integrating type wherein a capacitor is successively charged by an input signal and discharged by a reference signal, the time required for discharge serving as a measure of the amplitude of the input signal.

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Godalming, United Kingdom

Howard A Dorey