Abstract: A system includes radio devices where radio links between the devices are configured by bringing the radio devices in close proximity for a few seconds. A proximity detector of a radio device detects the proximity of another radio device and an automatic registration process begins to configure a link between the devices. One-to-one or one-to-many links may be established. Links may be cancelled by repeating the process. The devices may include an indicator to indicate establishment of the link.

Abstract: A system includes radio devices where radio links between the devices are configured by bringing the radio devices in close proximity for a few seconds. A proximity detector of a radio device detects the proximity of another radio device and an automatic registration process begins to configure a link between the devices. One-to-one or one-to-many links may be established. Links may be cancelled by repeating the process. The devices may include an indicator to indicate establishment of the link.

Abstract: A system includes radio devices where radio links between the devices are configured by bringing the radio devices in close proximity with hosts for a few seconds. A proximity detector in the device detects the proximity and an automatic registration process begins to configure a link between the device and nearby host. One-to-one or one-to-many links may be established. Links may be cancelled by repeating the process. The devices may include an indicator to indicate establishment of the link.

Abstract: A signalling system includes a plurality of active transponders (10), an interrogation station (12) and a source (14) of switching signals. Each of the transponders has a microcontroller (20), a radio transceiver (34) for responding to radio interrogation signals from the interrogation station, the radio transceiver being coupled to the controller by way of switching means (36) which switches the transceiver on or off whilst leaving the microcontroller active, and a passive receiver (38) for receiving switching signals from the source of switching signals which signals are used by the microcontroller for switching-on or -off the transceiver. Transducers (26, 28, 30) may be coupled to the microcontroller for monitoring environmental features, such as ambient temperature and humidity, and data relating to the features is stored in a RAM (32) in readiness to be relayed to storage means (56) in the interrogation station (12) as and when required.

Abstract: A superhet receiver in which an input signal is frequency down-converted in a first mixer (14) to produce a first IF signal comprising a wanted channel signal and an image channel signal. The first IF signal, without image rejection filtering, is frequency down-converted in a second mixer (24) to produce a second, lower IF signal comprising at least the wanted channel signal having a bandwidth corresponding to a predetermined passband of a channel filter (32) coupled to the output of the second mixer. The local oscillator signals used in the first and second frequency down conversion processes are varied in order to produce successively different image channel signals in the first IF signal and to maintain the wanted channel signal in the second IF signal within the passband of the channel filter (32).

Abstract: A low IF receiver frequency translates an input signal in quadrature related mixers, filters in respective low pass channel filters, and derotates to produce a wanted signal and its image. At switch-on, the receiver is operated as a zero IF receiver in order to determine which of the adjacent channels to the wanted channel has the smaller interferer, and the local oscillator frequency supplied to the mixers is then adjusted to bring that interferer into the channel bandwidth of the low pass channel filters.

Abstract: A superhet receiver in which an input signal is frequency down-converted in a first mixer (14) to produce a first IF signal comprising a wanted channel signal and an image channel signal. The first IF signal, without image rejection filtering, is frequency down-converted in a second mixer (24) to produce a second, lower IF signal comprising at least the wanted channel signal having a bandwidth corresponding to a predetermined passband of a channel filter (32) coupled to the output of the second mixer. The local oscillator signals used in the first and second frequency down conversion processes are varied in order to produce successively different image channel signals in the first IF signal and to maintain the wanted channel signal in the second IF signal within the passband of the channel filter (32).

Abstract: A signalling system includes a plurality of active transponders (10), an interrogation station (12) and a source (14) of switching signals. Each of the transponders has a microcontroller (20), a radio transceiver (34) for responding to radio interrogation signals from the interrogation station, the radio transceiver being coupled to the controller by way of switching means (36) which switches the transceiver on or off whilst leaving the microcontroller active, and a passive receiver (38) for receiving switching signals from the source of switching signals which signals are used by the microcontroller for switching-on or -off the transceiver. Transducers (26, 28, 30) may be coupled to the microcontroller for monitoring environmental features, such as ambient temperature and humidity, and data relating to the features is stored in a RAM (32) in readiness to be relayed to storage means (56) in the interrogation station (12) as and when required.

Abstract: A phasing receiver includes a quadrature mixing arrangement for frequency converting an input or high IF information signal to a pair of quadrature related low IF signals. The low IF signals are applied to a polyphase filter which functions as a low pass and adjacent channel rejection filter. One or more elements effecting a fine adjustment of relative phase away from quadrature and/or relative amplitude away from equality of the low IF signals are incorporated in information or oscillator signal paths in or about the mixing arrangement or a superhet stage preceding the quadrature mixing arrangement. These elements effect a predistortion of relative phase and/or relative amplitude of the low IF signals in order to compensate for mismatches in an input stage of the filter, and thereby improve image rejection by the filter.

Abstract: An automatic gain control strategy for zero IF receivers in which the gain of low pass filters (20,22) is altered whilst keeping their bandwidths substantially constant. The low pass filters (20,22) are implemented as gyrator filters, each of which comprise at least one pair of transconductors, the ratio of the transconductances of which are adjustable in such a manner as to maintain the product of their transconductances constant. An electronic signal for adjusting the ratio of the transconductances is derived from an estimate of the instantaneous signal amplitude of the received signal.

Abstract: A line deflection stage includes a line oscillator (LO), a driver (DR) and a line output transistor (TR1) the collector of which is connected through the parallel arrangement of a switching transistor (TR2) and a diode (D3) to a line deflection coil (Ly) and a scan capacitor (C.sub.s). The deflection coil (Ly) and scan capacitor (C.sub.s) are shunted by a diode (D2) while a flyback capacitor (C.sub.f) is connected across the emitter-collector path of transistor (TR1). The line oscillator (LO) output is also applied to an input of a flyback time controller (TC) which produces a pulse output under the control of a control input (C). This pulse output is amplified by a further transistor (TR3) and an associated transformer (T) and applied to the base of transistor (TR2) to cut this transistor off for a controlled part of the flyback period to prevent the flyback capacitor from immediately discharging and hence extend the flyback period.