Abstract: A quadrupole mass spectrometer comprises an ion source (20), a mass filter (22) and an ion collector (24). The ion source comprises an array (30) of quantum wires. The mass filter comprises four glass fibres (32) coated with nickel and the ion collector is an a electrode connected to an integrated complementary metal oxide semiconductor temperature compensated integrated amplifier.

Abstract: A solid sensor, for sensing a physical parameter such as pressure, comprises a resonantly vibratable beam formed across a cavity in a substrate by micro-machining, and arranged such that changes in the parameter vary its resonant frequency. The beam either consists of or has deposited on it a material exhibiting piezo-electric effect, so that vibration of the beam can be excited by using the effect. This is achieved using light, either by forming a photodiode in the substrate in or near the beam, so that illuminating the photodiode causes a voltage to be applied to the beam, or, in the case where the piezo-electric material exhibits surface piezo-electric effect, by directly illuminating the beam.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.