Abstract: A low power miniature repeater station is located on a vehicle such as a train, cargo ship, cruise ship or other vehicle which is expected to carry multiple paging receivers. The repeater station receives paging messages that originate as satellite signals and rebroadcasts them in the immediate vicinity of the vessel. The rebroadcast may typically be over a single FM carrier frequency or in the form of a subcarrier signal. The repeater includes an FM scanning receiver that samples the radio band and enables the rebroadcast of signals only if FM subcarrier signals are not detected within the vicinity of the vehicle. As the vehicle re-approaches a populated area, continued scanning of the radio band eventually detects the presence of subcarrier signals and shuts down the repeater to ensure that it will not interfere with licensed terrestrial broadcasters.

Abstract: The transmission system is designed for links between an infrastructure and moving bodies (10.sub.1, 10.sub.2) constrained to move along a determined path. The infrastructure has fixed transmitter/receiver stations distributed along the path, each having two transmitter/receivers allocated to two adjacent cells, e.g. (E'.sub.1, E.sub.2). The transmitters of two successive fixed stations allocated to the same cell are synchronized and they transmit using a coding system that is capable of tolerating or taking advantage of propagation over multiple paths.

Abstract: A bandwidth management system for a remote repeater network for modifying a first signal to create a second signal within the bandwidth of a communications link, transferring the second signal across the communications link, and reconstructing the first signal at the remote end of the communications link. The bandwidth management system featuring several mixing modes for performing the signal conversion and reconstruction. The system offering a calibration feature to correct for phase distortions introduced in reconstruction of the original signal. The calibration feature incorporating signals from a global positioning satellite system for reconstruction.

Abstract: A mobile satellite communication terminal capable of performing satellite communication both indoors and outdoors. In an indoor mode, the mobile satellite communication terminal includes an indoor terminal for carrying out transmission or reception of a signal through a ground radio link and a repeater terminal installed in such a location that the repeater terminal can get an unobstructed view of a satellite for carrying out transmission or reception of a signal through a satellite communication link. In an outdoor mode, an antenna of the indoor unit is replaced by an antenna for the satellite communication link, whereby the indoor terminal can be used as an outdoor terminal.

Abstract: Method and apparatus for enhancing diversity in spread spectrum type communication systems by creating pseudo-multipath conditions or links for certain communication signals. The invention provides alternative or additional signal paths, for signals being transferred between gateways and communication system users through one or more a satellite repeaters. These additional paths are used to establish and maintain adequate signal diversity as well as certain signal links by remote subscribers in heavy urban areas. In further aspects of the invention, diversity enhancers can employ high gain parabolic antennas and tracking mechanisms, or passive reflective surfaces. Signals can be relayed to subscriber units in canyon type blocked areas or within structures.

Abstract: A method, a mobile communication system and a mobile station for establishing a telecommunication connection on a direct mode channel and for improving radio coverage by way of using a simple and cheap repeater. An inexpensive and simple repeater is achieved by, instead of using two transceivers, using two receivers and just one transmitter. A mobile station, prepared for direct mode communication, is able to switch between channels answering to commands sent from the repeater.

Abstract: A small light weight modular microcomputer based computer and communications systems, designed for both portability and desktop uses. The systems make use of a relative large flat panel display device assembly (2), an expandable hinge device (10), battery power source (9), keyboard assembly (16), and wireless communications devices (32, 51). The systems are capable of bi-directional realtime communications of voice, audio, text, graphics and video data. Both wire-based or wireless communications methods and devices are implemented. Wireless communications devices may include one or more telephone-like handsets (14) and/or earset (34). The wireless communication devices may include one or more antennae (32). Systems can be configured in a portable arrangement similar to conventional notebook computers, but can be quickly and easily disassembled and re-assembled for office desktop uses.

Abstract: A communication apparatus used in a digital cordless telephone system, such as a personal headphone system (PHS) having a local base station and a local mode subscriber, in which, if the local mode subscriber is set for use in the local mode, the local mode subscriber can respond to signals of the public mode. If the local base station receives incoming call signals of the public mode from a public base station, the received call signals are transferred from the local base station to the local mode subscriber. This enables the incoming call signals from the public base station to be received via the public base station by the local mode subscriber even if the latter is in the local mode. If, with the local mode subscriber set to the local mode, the local base station receives incoming call signals of the public mode from the public base station, the local base station transmits the call signals to the local mode subscriber.

Abstract: In a radio paging system, first and second radio units perform radio communication via a relay station. This system includes a radio selective paging receiver for receiving a radio wave from the relay station and generating a ringing tone to call a callee at the second radio unit when the first radio unit calls the second radio unit.

Abstract: Control circuitry and an associated method for a modified-user, wireless communications system, such as a cellular communication system wherein groups of mobile transceiver units are positioned to travel together. Circuitry is positioned to travel together with the group of mobile transceiver units and to generate common control requests to control operation of the entire group of mobile transceiver units. When embodied in a cellular communication system, a common hand-off request is generated for the entire group of mobile transceiver units, obviating the need for each transceiver unit to independently generate a hand-off request. If a mobile transceiver is operable pursuant to an air interface standard dissimilar to a fixed-site transceiver with which communications are to be effectuated, a converter converts communication signals so that the communication signals can be communicated therebetween.

Abstract: A system for enhancing speech intelligibility using wireless communication is provided. The system has a number of talker units, each having a microphone and a transmitter so that an audio input received at the microphone is transmitted via the transmitter as an output. The system includes a receiver unit having a receiver to receive the outputs of the talker units, and a mixer to mix the outputs to form a mixed output signal, and a transmitter to transmit the mixed output signal on a preselected frequency. The system also has a listener unit tunable to receive the mixed output signal transmitted on the preselected frequency. The system can be embodied in a serial daisy chain arrangement or in a parallel repeater arrangement. A method for enhancing speech intelligibility using wireless communication is provided.

Abstract: A local resource controller (409) from among a plurality of local resource controllers, receives a service request sourced by a communication unit (411). The local resource controller (409) selects (503) any one of at least two service controllers (301, 303, 305) where the service request is to be routed. The service request is routed to the first service controller (505) via a network (307), which is coupled to the service controllers (301, 303, 305) and the plurality of local resource controllers (409).

Abstract: An incoming calling system of the present invention purposes to securely notify the user of the incoming to a radio portable terminal of a mobile communication unit or the like without disturbing others and decrease the probability of erroneous notification. Therefore, an incoming notification signal transmitter (24) for notifying the user of incoming can detect an incoming tone by inserting a jack into and connecting it with an earphone-microphone terminal (23) provided for a portable telephone (21) side and moreover, an incoming notification signal transmitter (24) is set to and supported by portable telephone (21). When portable telephone (21) receives an incoming call signal according to incoming calling from a base station (22), it generates a speech signal of an incoming tone and the speech signal is input to the incoming notification signal transmitter (24) through the earphone-microphone terminal (23) to detect incoming.

Abstract: A method and apparatus for a communication system (100) to register groups of co-located users in a mobile vehicle (110) involves collecting (200) registration information for multiple users by a Vehicle Communications Control Unit (500) (VCCU) on board the mobile vehicle (110), creating (202) at least one group registration request message by the VCCU (500), and sending the at least one group registration request message to an Earth Terminal (102) (ET) of the communication system (100). After the communication system (100) registers each user whose registration information is contained within the at least one group registration request message, the ET (102) sends (312) at least one group registration response message to the VCCU (500), where the message includes information describing whether each registration attempt was successful. The VCCU (500) can then inform (210) each user as to the status of the registration attempt.

Abstract: In a conventional Time Division Multiple Access (TDMA) wireless system, the specified distance between a mobile unit and the base transceiver system (BTS) cannot exceed predetermined distances because of time slot synchronization constraints. In this approach to extending TDMA system coverage, in-band translator components are located in the center of remote cells which would normally contain a base transceiver system (BTS). The in-band translators include a loop back circuit that permits a host BTS to measure the propagation time delay by sending test access signals between the host BTS and each in-band translator. The measurements are then used to adjust a time delay in an uplink signal as received from each in-band translator by the BTS in normal operation.

Abstract: A first portable subscriber unit (122, 602) of a plurality of portable subscriber units transmits (504) an inbound message (400) on an inbound channel. The inbound message is intended for a base receiver (616). The inbound message is received (506) by a second portable subscriber unit (606, 608) of the plurality of portable subscriber units. The second portable subscriber unit retransmits (520) the inbound message on the inbound channel only when a predetermined attribute of the inbound message satisfies (508, 510, 512, 514, 518) a predetermined condition.

Abstract: The present invention relates to a mobile cellular phone, the mobile cellular phone including: a radio handset and a mobile cellular phone body for transmitting and receiving a sound and a signal information through a wireless channel; and a holder disposed in the body for accommodating the radio handset so that when the radio handset is detached from the holder the body can relay the sound and the signal information between the radio handset and a base station to thereby enable a telecommunication to be realized through the radio handset and when the radio handset is accommodated in the holder, the telecommunication can be realized through the body.

Abstract: Satellite telecommunications repeaters are provided which receive, amplify, and locally retransmit the downlink signal received from a satellite thereby increasing the effective downlink margin in the vicinity of the satellite telecommunications repeaters and allowing an increase the penetration of uplink and downlink signals into buildings, foliage, transportation vehicles, and other objects which can reduce link margin. Both portable and non-portable repeaters are provided.

Abstract: A local telecommunications network is provided for satellite based telecommunications. The network 10 includes multiple handsets 18-22, 50 and 54 which communicate directly with ground stations 14 and 16. The ground stations communicate with an overhead satellite 12 through a satellite telecommunications uplink. The ground stations include a router for determining whether outgoing calls are directed to a destination handset located within or outside a predefined local geographic cell 30 and 32 for the corresponding ground station 14 and 16. If the destination handset is located outside the local cell of the originating handset, the ground station passes the call to the overhead satellite 12 to establish a satellite telecommunications link. However, if the destination handset 50 is located within the same local cell 32 as the originating handset 22, then the router 16 establishes a direct link between the handsets 22 and 50 without establishing a satellite telecommunications link 26.

Abstract: An accessory apparatus for mobile radio telephones, particularly those used in cellular networks, permits utilization of the full communication range capability of a vehicle-mounted cellular radio telephone by a cordless portable handset remote from the vehicle. The apparatus includes a plug-in adapter unit located in a vehicle and interconnected between the existing handset and transceiver of the vehicle-mounted radio telephone. The adapter unit includes a first, resident, down-link transceiver operating at radio frequencies outside of the cellular frequency band, and adapted to receive demodulated audio and/or data signals from the resident cellular transceiver, and retransmit the signals via a low-power modulated down-link RF carrier signal to a portable remote cordless handset/transceiver.

Abstract: A mobile terminal for satellite communication of voice data, facsimile and computer information, which consists of an RF transceiver section, and a processor board. The processor board has two digital signal processors and a multi-task control processor for controlling the operation of the two signal processors. Net radio service is implemented in the mobile terminal and includes a priority 1 mode wherein a channel search is performed on a net radio channel database for an available channel if any problem is initially encountered in obtaining control of a specific communication channel such as a channel currently in use or a channel designated for use as a default channel.

Abstract: The invention provides a system and method whereby a mobile station of telecommunications system selects one of a number of fixed ground stations by which the mobile station communicates with the public switched telephone network or other such system, selection being made by the mobile station receiving selected criteria and deriving from a plurality of these criteria a score for each of a plurality of the fixed stations, the fixed station via which communication is to be made being selected in dependence upon the score derived for that fixed station.

Abstract: An RF repeater for exchanging time division multiple access (TDMA) transmit and receive signals between a mobile handset and a CATV plant or other signal conduit has a signal timing detector responsive to the timing of transmit signals being broadcast to the handset to provide timing information indicative of the timing of receive signals being received from the handset. A signal level detector responsive to the signal level of the receive signals provides signal level information. A signal control device responsive to the timing information and the signal level information provides a signal level control output for time slotted control of the receive signals. The timing and signal level information may be used to effect diversity selection between receive signals from two spaced antennas at the repeater and/or diversity selection may be effected between two versions of the receive signal at a base station after passing through the signal conduit.

Abstract: Control circuitry and an associated method for a modified-user, wireless communications system, such as a cellular communication system were in groups of mobile transceiver units are positioned to travel together. Circuitry is positioned to travel together with the group of mobile transceiver units and to generate common control requests to control operation of the entire group of mobile transceiver units. When embodied in a cellular communication system, a common hand-off request is generated for the entire group of mobile transceiver units, auguating the need for each transceiver unit to independently generate a hand-off request.

Abstract: An CDMA telephone system, an RF repeater is connected through a CATV plant and a RASP to a base station and exchanges radio signals with a mobile handset. The base station includes a RAKE receiver and the RF repeater employs a pair of receive signal paths and a pair of transmit signal paths, each with a delay line in one, to provide transmit and receive antenna diversity without doubling the band with the CATV plant.

Abstract: In a communication environment (140) having multiple vehicular repeater systems (110, 120) operating according to a priority scheme designating primary responsibility for retransmitting signals, a vehicular repeater system (120) supports automatic transitioning from a non-priority mode to a priority mode (410, 420). The vehicular repeater system (120), when operating in a non-priority mode, detects that a communication signal was submitted for retransmission by a priority vehicular repeater system (440), and monitors for a particular time period to detect an acknowledgment signal (450). When no acknowledgment signal is detected within the particular period, the priority scheme is modified, preferably such that the non-priority vehicular repeater assumes priority repeater status (460).

Abstract: The present invention relates to a method and radio system for controlling a subscriber station (MS1) operating on a direct mode channel in a radio system, said radio system comprising a radio network (SwMi) with at least one base station (BS) and subscriber stations (MS1), and further, at least one repeater station (RS), which forwards traffic between said at least one base station (BS) and the subscriber stations (MS1) operating on the direct mode channel. To control the subscriber stations operating on the direct mode channel, information on the identifiers of subscriber stations operating on the direct mode channel in the coverage area of the repeater station (RS) is maintained in said repeater station (RS).

Abstract: In a radio data communication network where a plurality of radio data communication apparatuses mutually communicate information through frames carried by radio waves, a communication method using radio data communication apparatuses having a relay function is provided. When two radio data communication apparatuses cannot directly communicate with each other due to the limit of the radio wave range, another radio data communication apparatus serves as a relay station to relay frames between the two apparatuses, thus extending a communicable range.

Abstract: A method for defining a radio frequency map to be used to isolate negative effects of undesirable radio frequency emitters on radio device communications handheld and stationary. The method includes the steps of measuring C-band power corresponding to an L-band beam as part of an L-band footprint of a communication satellite, calculating various identifiable interference errors associated with the signal transmission path, and subtracting the interference errors from the original C-band power measurement resulting in a power value corresponding to undesirable radio frequency emitter interference at the location of the L-band beam. The resultant radio frequency map can then be used to reallocate frequency channels of operation used by radio devices, mobile phones for example, resulting in power savings in the radio device while maintaining a suitable signal-to-noise ratio.

Abstract: Like a conventional one-way pager system, a two-way pager system is provided in which a message is received by paging from a base station and a message responding to the received message is returned to the base station. In this system, direct communication and peer-to-peer communication between terminals are performed. All the terminals included in the service area of the base station are always synchronized with sync signals paged from the base station. No special infrastructure is therefore required for synchronizing the terminals with the sync signals to perform the peer-to-peer communication. Furthermore, since each of the terminals receives a paging signal during the peer-to-peer communication, it can respond to a paging call.

Abstract: An internetworking node for providing internetworking services for mobile wireless nodes. Each mobile wireless node is associated with at the most one internetworking node. Each mobile wireless node selects which internetworking node it will associate with. The internetworking node will then act for all wireless nodes associated to it in relaying messages between wireless nodes or between a wired Local Area Network (LAN) and the wireless nodes.

Abstract: The invention relates to a method of establishing a call in a mobile communications system and to a mobile communication system comprising at least one base station, mobile stations communicating with the mobile communication system and marked at least with system addresses, mobile stations communicating on a direct mode channel and marked with direct mode addresses, and at least one repeater station which transmits traffic between said at least one base station and the mobile stations, communicating on the direct mode channel. To provide flexible call setup, the repeater station comprises a conversion table for converting between said system addresses of the mobile stations and said direct mode addresses.

Abstract: A system for recording vehicle data from vehicles traversing a test track includes a plurality of locator beacons buried in respective well casings around the test track for transmitting location signals. Each beacon includes a transmitter and a microprocessor that controls the transmitter. Receivers are disposed in the test vehicles for receiving the location signals as the vehicles pass by the beacons, and a respective computer receives the position signals from each receiver and formats the signals as appropriate for the vehicle's onboard flight recorder. Then, after checking for signal fidelity the computer sends each signal to the flight recorder, which time stamps the position signals along with other data collected from the vehicle. In this way, data can be correlated to particular segments of the test track.

Abstract: For use in a wireless computer network having a radio relay capable of transmitting messages, a system and method, operable with the radio relay, for selectively repeating a unicast message received from a source end-station only upon some indication that a destination end-station has not received the message. The system includes: (1) a transceiver that receives the unicast message from the source end-station and (2) control circuitry, coupled to the transceiver, that determines whether the destination end-station has received the unicast message and causes the transceiver to refrain from repeating the unicast message if the destination end-station has received the unicast message, the radio relay thereby freed from repeating already-received unicast messages.

Abstract: An emergency routing protocol within a wireless communication network. A mobile device can establish a communication link to the system backbone even when, for whatever reason, it can no longer communicate directly with a base station. The emergency routing protocol enables a distressed mobile device to communicate with the system backbone through another mobile device serving as an intermediary. The intermediary mobile device forwards information destined to/received from the distressed mobile device to its intended destination.

Abstract: The present invention relates to a device 1 for allowing the use in a aircraft A of at least one radio communication apparatus (R), such as mobile telephones. According to the invention, the radio communication apparatus (R) includes a first connection switch (MC1) between an information processing unit (2) and a transmit unit (3), and a connection switch (MC2) between the processing unit (2) and a receiving unit (5), and the device (1) includes a transmitter (8) transmitting waves (OE) out of the aircraft (A), a receiver (10) detecting waves outside the aircraft (A), and paths L1 and L2 respectively linked to the transmitter (8) and to the first connection switch (MC1) and to the receiver (10) and to the second connection switch (MC2).

Abstract: A method and the corresponding messaging system of selecting a transmitter for directed message delivery set is a messaging system including a plurality of transmitters arranged and constructed to operate in a simulcast or non-simulcast mode, the method including directing a first and a second transmitter to transmit in the simulcast mode, respectively, a first signal including a reference parameter and a first identification signal and a second signal including the reference parameter and a second identification signal, the first identification signal and the second identification signal distinguished from the reference parameter by, respectively, a first and a second predetermined amount, and receiving an acknowledgment signal that includes a indication of the first identification signal relative to the second identification signal or both relative to a threshold as determined at a messaging unit location, the indication corresponding to a preferred transmitter, selected from the first and the second transm

Abstract: A base station (BS) communicates with a plurality of mobile users in a platform. In one embodiment, the base station and mobile services center (MSC) associates all the mobile users with the platform. The BS and MSC then associate a movement of the platform from one cell to another with a handoff of all the mobile users in the platform. The handoff is complete while the overhead is minimized. Exemplary embodiments are provided for use with the Advanced Mobile Phone Service (AMPS) protocol.

Abstract: A broadcast transmitter for generating low power modulated signals, especially for a wireless speaker system. A signal source such as a source of composite audio signals including left and right audio signals and a pilot signal are applied to a radio frequency signal oscillator. The radio frequency signal oscillator includes a bipolar transistor connected in a common base configuration, and having a stripline element as a frequency determinative component in the collector circuit of the bipolar transistor. The modulating signal is applied to the base of the bipolar transistor which modulates the collector junction capacitance of the transistor thereby frequency modulating the signal produced by the oscillator. Varactor tuning is provided for setting a nominal frequency of oscillation.

Abstract: In order that communication may be performed independently of indoors or outdoors, in this mobile satellite communication terminal, when it is used indoors, the indoor terminal transmitting and receiving a signal in the ground radio channel is connected to the repeater terminal installed at a position from which the satellite can be seen by the ground radio channel, further, the repeater terminal communicates with the satellite by using the satellite channel. On the other hand, when it is used outdoors, the outdoor terminal is constituted by mounting the outdoor unit for the satellite channel consisting of the antenna for the satellite channel and the radio frequency section instead of the indoor unit consisting of the antenna for the ground radio channel and the radio frequency section of the indoor terminal.

Abstract: A vibration unit is for use in combination with a portable telephone apparatus having a holding mode in which connection is held between the portable telephone apparatus and a base station assigned to the portable telephone apparatus. The portable telephone apparatus transmits a reception information signal in response to reception of an incoming call signal directed to the portable telephone apparatus. Supplied with the reception information signal, the vibration unit makes a vibrator vibrate to announce reception of the incoming call signal to a user of the portable telephone apparatus. When operated by the user, a holding switch produces a switch operation signal. In response to the switch operation signal, a unit control section controls to make a unit radio section transmit a holding indication signal towards the portable telephone apparatus. Supplied with the holding indication signal, the portable telephone apparatus is put in the holding mode.

Abstract: A pager/ringer system for permitting co-operative emission relay between a plurality of user terminals of a satellite personal communication network (S-PCN) service. Each user terminal includes a receiver, a transmitter, a memory storage device and a unique address. By permitting relay between user terminals, the S-PCN will achieve improved dependability in signal-blocking environments by exploiting the spatial diversity of satellite signal strength.

Abstract: A vehicular repeater system communicates with a portable mobile radio using the same RF communication band and digital trunking protocol that it communicates with a base site. The repeater station may employ an operational radio within a vehicle which communicates with the base site. A separate repeater radio module is connected to the operational radio, preferably through hardwired links. The separate repeater radio module includes a transmitting section which receives messages from the base site through the operational radio, and forwards these messages through a passive RF interface to a portable radio. The separate repeater also includes a receiving section which receives messages from the portable radio, and forwards these messages through the operational radio to the base site.

Abstract: A communication system (100) for dynamically selecting transmitters (115) for message transmission includes the transmitters (115) for sending transmission signals and a portable messaging unit (105) for receiving the transmission signals, calculating signal strengths of the transmission signals, and transmitting a signal indicative of the signal strengths. A controller (110) receives the signal and determines therefrom carrier-to-interference (C/I) values indicative of relative strengths of the transmission signals received by the portable messaging unit (105). Prior to message delivery, the controller (110) determines a selected transmitter (115) for transmitting a message to the portable messaging unit (105). The selected transmitter (115) is associated with a lowest C/I value that is chosen from the C/I values and that exceeds a C/I threshold value.

Abstract: In a mobile communication network comprising a base station (11) having a service area (13) and a plurality of mobile stations, communication is rendered possible between the base station, with a first station (15(1)) in the service area used as a repeater station, and a second station (15(2)) which may be present near or beyond a boundary of the service area. It is presumed that the mobile stations are operable with battery saving and that such a repeater station exists in a communication area (17) of the second station put into full operation. Preferably, the mobile communication network is operable with time division multiplexing, with each frame composed of a predetermined number of time slots.

Abstract: A cordless telephone apparatus has a base station connected to a public telephone network and assigned with a specific identification code and one or more personal stations linked to the base station through the medium of radio frequencies. The base station has one or more additional functions in addition to the speech function. The personal station can perform radio communications with the base station within a range in which radio waves from the base station is receivable and can perform radio communications with a cell station connected to a public telephone network outside the radio wave receivable range. The personal station has a remote-control instruction unit for instructing operation of the additional function of the base station.

Abstract: A mobile phone set includes a base unit and at least one handset belonging to the base unit. In the base unit, a receiving section 11 receives a first modulated wave S.sub.1 which is a digital modulated wave from TX 3, and a demodulating section 12 demodulates the received wave, and further a decoding section 13 decodes the demodulated wave. Further, a detecting section 17 detects the demodulated wave. Further, a detecting section 17 detects that the decoded signal is of a calling signal for the handsets 2-1 and 2-2 associated with the base unit, and after the detection a controlling section 25 instructs a D/A converting section 14 to D/a convert a digital signal decoded by the decoding section 13 to an analog signal and a modulating section 15 to modulate the analog signal. A transmitting section 16 transmits a second modulated wave S.sub.2 as the analog modulated wave to the handset 2-1 or 2-2. Further, in the base unit 1, a receiving section 18 receives a third modulated wave S.sub.

Abstract: A wireless base station operating in a system in which wireless base stations are used to provide a link between a remote fixed part and a handset and method of operation of the same. The wireless base station prevents unnecessary handover initiation by the handset in the event that the link between the wireless base station and remote fixed part is poor.

Abstract: A phase modulator having a Gilbert cell mixer can be used in frequency ranges from a microwave frequency band of several GHz to a millimeter wave band of several 10 GHz. Two output signals Vout1, Vout2 from the Gilbert cell mixer are supplied to balanced input terminals of a balanced-to-unbalanced converter, which produces a phase-modulated output signal Vout from an unbalanced output terminal thereof. Even when a differential amplifier comprising FETs Q1, Q3 and a differential amplifier comprising FETs Q2, Q4 do not operate symmetrically, the phase modulator generates phase-modulated output signals that have the same amplitude as each other and are in opposite phase to each other. With the Gilbert cell mixer comprising FETs, the phase modulator can be used in the frequency ranges described above. If the balanced-to-unbalanced converter is in the form of a planar circuit, then the phase modulator may be implemented by an MMIC.

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.