Shaye Communications Limited

At&t Wireless Communications Products Limited

British Telecommunications Public Limited Company

Stc, Inc

Gec Plessey Telecommunications Limited

Orbitel Mobile Communications Limited

Sinclair Research Limited

Mercury Communications Limited

Phonepoint Limited

Ferranti Creditphone Limited

Lucent Techonolgies Wireless Limited

Graham E Beesley

Nigel Everard Barnes

Peter N Proctor

Rupert Goodings

David C Odhams

David J McCabe

Michael T Dudek

Ian Rodgers

Malcolm Crisp

Chris Cant

Jasjit S Saini

Richard Albrow

A telecommunications system having at least one base unit and a plurality of portable units is arranged to enable automatic re-registration of a portable unit with the system. The portable unit includes system and unit identity detectors and a registration sequence generator. The registration sequence generator is connected to a timer which monitors the elapse of time since a signal from a base unit of the system intended for the portable unit is received. The registration sequence generator generates a re-registration request in the event the monitored elapse of time is greater than a predetermined period and a signal from a base unit of the system is received which is not intended for the portable unit. With the system described portable units can automatically re-register with the system after being out of range of a base unit without the need for a separate beacon signal.

Telecommunications system

Telecommunications system having single base unit and plural individual

Method of establishing a communication link in a digital cordless

A problem arises in electronic equipment incorporating a display, such as an LCD display, which is not intrinsically illuminated. The present invention provides a controlled backlight for such displays, and is particularly useful in battery-powered equipment where power consumption must be kept to a minimum. The circuitry comprises a display 1 controlled via a conventional display driver 6 from other equipment (not shown) such as a microprocessor. Whenever the display is changed a signal is sent also to a timer circuit 7 which triggers, and passes a control signal to an electronic switch 4 which in turn passes power from a battery 3 to a lamp 2. The lamp 2 is arranged to illuminate the display 1. After a preset period, the timer circuit 7 sends a further control signal to the switch 4 to switch lamp 2 off.

Illumination of displays with control which switches illuminator in

Technique for time-division duplex cordless telecommunication

A time division duplex transceiver incorporating a dual conversion superheterodyne receiver, and in which the first receiver local oscillator doubles as the frequency source for the transmitter. The oscillator is a voltage controlled oscillator VCO forming part of a mixer-type phase locked loop. Frequency deviation in the loop is achieved by mixing the VCO output with a selected harmonic of the output of the second receiver local oscillator. The reference oscillator is a crystal controlled oscillator whose output is switched as between transmit mode and receive mode at a switch before being passed to the loop phase detector. The transceiver is able to rapidly and repeatedly alternate between transmit and receive modes and is thus well suited to time division multiplex operation.

Single frequency time division duplex transceiver

A method of establishing a digital time-division duplex radio communication link between one of a plurality of portable units and a base unit in a cordless telephone system, transmissions from the base unit are allowed only on a ping-pong basis with transmission bursts from all the active transmitters in the base unit being synchronized with one another. This prevents blocking of receiver sections due to co-sited transmitters transmitting at the same time on a different channel. The difficulty of synchronizing the transmission bursts of the active portable units with their respective transceivers within the base unit is overcome by allowing the portable unit to make an initial continuous call comprising multiple identical sequences of data containing units small enough to be completely received within the limited reception windows of the base unit. After the initial call has started communication, an exchange of signals takes place on a ping-pong basis to establish synchronism between the portable unit and base unit. Finally, if all is well, the system reverts to a speech mode in which voice signals rather than data signals are exchanged between the portable unit and base unit.

Duplex communications method and system

An amplifier for use in the I.F. stages of an F.M. radio receiver comprises several identical direct-coupled stages 2,4,6 each comprising common emitter transistors 8 and inductive loads 10.

F.M. Amplifier for use in I.F. Stages

Growing community of inventors

Winchester, United Kingdom

Graham E Beesley