Abstract: A cellular radio telephone system comprises a mobile cellular telephone (1) adapted to have a hand portable telephone (2) containing a number assignment module, i.e. a NAM (7), removably connected thereto. The mobile telephone (1) has a microprocessor (4) which can access the information stored in the NAM (7) of the hand portable telephone (2) either directly or via a memory 16 whereby the mobile automatically assumes the telephone number of the hand portable telephone when the two telephones are connected together. Hence a subscriber need only have a single billing account for both telephones. Also, the same mobile telephone may be used as a host at different times by any number of subscribers having their own hand portable telephones. Each subscriber will be able to receive his own calls and the charges for using the system can be levied to the appropriate subscriber's account.

Abstract: A method of receiving digitized data encoded to permit forward error correction, for example convolutionally encoded data transmitted in a burst-mode radio communication system such as GSM. Prior to transmission a set of first data elements (bits) relating to a first message which may be associated with a first channel type (e.g. a traffic channel (TCH) in GSM) has selected bits substituted or stolen by data elements (bits) relating to a second message which may be associated with a second channel type (e.g. a fast associated channel (FACCH) in GSM). At the receiver the second message is recovered by extracting the substitute data elements. In order to improve bit error rate performance the received data is then modified by replacing the substitute data elements with low-or zero-valued "soft decisions", i.e. further data elements comprising respective components indicative of the low level of confidence associated therewith relative to the original data element.

Abstract: A maximum likelihood detector using the Viterbi algorithm for estimating a sequence of data bits received over a communication channel. Depending on the constraint length (C), a plurality of different states is associated with the transmitted bits (e.g. 16 if C=4). The detector comprises various data sources relating respectively to state transition probabilities (branch metrics, previous partial path metrics) and observed values of the received bits. Means are provided for calculating the partial path metrics for each state using values from said data sources. The calculating means comprise a common adder/accumulator for performing repeated additive arithmetic operations and for storing the cumulative result thereof. Multiplexing means are also provided for selectively coupling the data sources in a predetermined order to the adder/accumulator to implement the partial path metric calculation.

Abstract: A transceiver for a cellular telephone, particularly a portable telephone, comprises a transmitter and a receiver coupled to a common antenna by an antenna duplex filter. The duplex filter comprises two passband filters connected respectively to the transmitter and the receiver. The receiver comprises a first amplifier. A notch filter tuned to the transmit frequency is connected to the output of the amplifier. The notch filter enables the filtering performance of the receive filter to be relaxed, and the location of the notch filter(s) at the output of amplifier means that the insertion loss is less critical. The requirement for lower filtering performance enables the duplex filter to be smaller and less costly.

Abstract: A cellular radio telephone system comprises a mobile cellular telephone (1) adapted to have a hand portable telephone (2) containing a number assignment module, i.e. a NAM (7), removably connected thereto. The mobile telephone (1) has a microprocessor (4) which can access the information stored in the NAM (7) of the hand portable telephone (2) either directly or via a memory 16 whereby the mobile automatically assumes the telephone number of the hand portable telephone when the two telephones are connected together. Hence a subscriber need only have a single billing account for both telephones. Also, the same mobile telephone may be used as a host at different times by any number of subscribers having their own hand portable telephones. Each subscriber will be able to receive his own calls and the charges for using the system can be levied to the appropriate subscriber's account.

Abstract: A tunable bandstop/bandpass filter particularly suitable for use in duplex applications where the transmit and receive bands are closely located, comprises two or more reactively coupled quarter wavelength resonators e.g. dielectric resonators. One end of each resonator is coupled to ground potential. The opposite (open-circuit) end of the resonators is coupled to adjacent resonators via coupling capacitors. Voltage controlled tuning means, e.g. a varactor and series connected capacitor, are coupled in parallel to the open circuit end of each of the resonators respectively. The stopband/passband of the filter can thus be adjusted by varying the voltage applied to the tuning means. Additionally, in the case of a bandpass filter a tunable zero (or "notch") may be introduced into the transmission response by including varactors coupled in series to the open-circuit end of the resonators.

Abstract: A magnetic catch comprises a magnetic assembly and a catch plate. The magnetic assembly includes a magnet flanked by two pole shoes. The magnet and pole shoes are biassed against a casing portion by an abutment feature provided integrally on a support member which is retained by resilient clips extending from the casing. The localized nature of the abutment feature provides a gap between the pole plates and the support member. This gap allows the pole members to move relative to the magnet so that they can align themselves with the catch plate to provide optimal physical contact therewith. Nevertheless, the biasing arrangement holds the magnet in a fixed position which helps to prevent the magnet and pole shoes from rattling.

Abstract: A compact portable telephone comprises a housing having a main body and an extending sleeve-like portion mounted for longitudinal slidable movement between a retracted position when not in use (see FIG. 2), and an extended position (see FIG. 1) for use. In a preferred arrangement, the earphone is present in the main body and the microphone is in the extending portion. The telephone includes a plurality of buttons or keys which can be selectively actuated for operating the telephone, and in one embodiment the extending portion is adapted to conceal selected ones of the buttons or keys when it is in the closed position to prevent accidental actuation of these buttons or keys.

Abstract: A two-piece transceiver housing for a mobile telephone comprises an open-topped box and a separate lid both made of conductive material, specifically diecast aluminium. A plurality of flat projections are formed integrally on the underside of the lid. These projections are arranged to bear internally against the side wall of the box when the lid is in place to prevent radio frequency radiation escaping from the housing without the need for a separate sealing component. The projections have a tapering curvilinear or rectilinear profile. This helps to distribute the stress and enables the projections to suffer slight deflection without breaking even when they are made of cast aluminium which is relatively brittle.

Abstract: A light guide for illuminating a keyboard or keypad from behind comprises a transparent grid-like plate having an array of apertures in each of which is accommodated a respective key of the keyboard/keypad. Means are provided for reflecting light from an external source into the plan of the light guide. The individual apertures are surrounded by an upstanding rib formed integrally with the light guide. The top (outer) face of the rib is rendered optically imperfect to promote the escape of light thereform, thus providing an illuminated ring around each key.

Abstract: An adapter (13) for enabling an external antenna, e.g. an antenna fitted to a vehicle, to be connected in place of an existing antenna (7) on a radio, particularly a portable radio telephone (1). The adapter is slidably located in a passageway (6) which may be part of an integral moulding of a radio casing (2). The existing antenna (7) may be slidably located in the passageway such that it can be displaced and so disconnected from the radio when the adapter is fitted. Alteratively, the radio has an internal existing antenna which is switched out when the adapter makes an external antenna connection, e.g., by means of contacts (15,16) mounted in the adapter and in the passageway (FIGS. 3 and 4). The slidable antenna (7) may be in the form of a tape having a bowed cross-section.