Abstract: A housing having sides interlocking at the corners is disclosed in which covers are provided inwardly curved edges having a G-shaped cross-section which slideably mate with a curved edge and inside slot of a side structured member of the housing. Upon fastening, a volume is created within the mated joints to captivate chips and burrs generated by the fastening process.

Abstract: A method and apparatus for determining which sector antenna of a sectorized cellular radiotelephone system is receiving the strongest radio signal is disclosed. The signal strength of sector antennas is sequentially sampled, converted to digital representations, and stored according to which antenna received the signal. The digital representations are recalled from storage and the strongest signal along with an identification of the receiving antenna are determined. This determination may be used in the handoff process or in detecting when a remote unit requires a handoff.

Abstract: A microstrip circulator is disclosed in which a resonator (311) is metalized on one layer (309) of a multilayer printed circuit board (301) and a ferrite element (305) is disposed in another layer (303) of the circuit board. Input/output port termination mismatch due to port lead misalignment is eliminated and ferrite to resonator coupling is accomplished in a simple and repeatable manner.

Abstract: A two way radio system employing power control of a remote station transmitter to produce a predetermined received signal level at a fixed site after handoff of the remote station from one radio channel to another is disclosed. A signal strength measurement is made on the in-use channel and a power level for the remote station transmitter is calculated from the measured signal strength, a predetermined nominal signal strength desired on the target radio channel, and a linear correlation of signal strength and remote station power level steps. The calculated remote station power level is then transmitted to the remote station as part of a handoff command.

Abstract: A fixed site station for cellular systems is disclosed. A plurality of radio transceivers are removably disposed in apertures of the common equipment housing and are provided unique parameters of operation by the system controller dependent upon the aperture in which the transceiver is located and the antenna configuration of the cell being served.

Abstract: A multiresonator dielectric block filter is disclosed in which capacitive coupling between foreshortened resonators disposed in the dielectric block is controlled by an electrode strip coupled to the conductive material covering the majority of the dielectric block surface. The electrode strip extends at least partially between two adjacent resonators to control the capacitive coupling between the resonators.

Abstract: An arrangement for releasably retaining a telephone apparatus in a standby condition includes a handset including an earpiece and a base having a shelf portion for receiving the earpiece. A hooking post member protrudes through the shelf portion and includes an integral spring to enable the hooking post member to be resiliently movable towards and away from the shelf portion. A switch hook which is separate from the hooking post is arranged to be actuated by the earpiece when the earpiece is brought into engagement with the base. When the earpiece engages the base shelf portion, the hooking post member is resiliently urged into contact with the earpiece for releasably retaining the earpiece on the base. A guide on the base prevents the hooking post member from twisting or rotating.

Abstract: A portable radiotelephone is disclosed in which an associated logic unit communicates via a data bus with an internal keypad and display and a detachable external keypad and display. Capability is provided for detecting the presence of the external keypad on the data bus and, in response to the detection, the information which would normally be communicated between the logic unit and the internal keypad and display is diverted to the external keypad and display. When the external keypad is detached from the data bus, communications between the logic unit and the internal keypad and display is reestablished.

Abstract: A telephone interconnect system for a two-way radio communications system is disclosed. A telephone patch interconnect unit accepts dialed digits from a telephone line, encodes them into a data packet, and couples the data packet to a fixed transceiver for transmission to remote units. A remote unit with a digit sequence identification matching the received and decoded dialed digit activates an alert. A remote unit may generate and store digits corresponding to a desired telephone number. The digits are subsequently encoded into a data packet and transmitted to the telephone patch interconnect unit. The interconnect unit accepts, acknowledges and decodes the data packet and couples the resulting digits to the telephone line.

Abstract: An overdissipation protection circuit for a semiconductor switch is disclosed in which the switch circuit is converted into a relaxation oscillator when the current drawn by the load exceeds a predetermined value. Dissipation in the switch semiconductor is reduced because it remains on only for a brief period of time during the relaxation oscillator cycle. If the current drawn by the load exceeds a second predetermined value, the semiconductor switch is turned off. The protection circuit is automatically reset when the relaxation oscillator reaches an on state and the current drawn by the load does not exceed the predetermined value.

Abstract: A method and apparatus for coordinating the transfer of communications control from one independent radio communications system to another is disclosed. A remote unit which communicates data messages is associated with a home system which has a plurality of fixed sites and overlapping radio coverage areas. As the remote unit travels away from its home system, communications may be maintained by providing radio coverage from an independent roam system. The last message received by the home and roam systems from the remote unit has the associated radio signal strength and time of reception stored at each system. When a current message is transmitted by the remote unit and both the home and the roam system receive the message, the roam system time stamps the message and calculates the signal strength associated with the current message.

Abstract: An automatic clock recovery circuit is described. The automatic clock recovery circuit samples a received data signal with a recovered clock signal and advances or retards the recovered clock signal based on the comparison between the received data signal and the recovered clock signal. The automatic clock recovery circuit selectively cancels advance or retard corrections in the presence of bias distortion and phase ambiguities to improve the lock acquisition time for recovered clock.

Abstract: The remote control system having symmetrical signaling circuits for radio communications is coupled to a single wire line/audio channel and permits two or more units, base stations and/or remote consoles, to be coupled to the single wire line. Each signaling circuit comprises a wire line coupler for coupling to the wire line, an audio input line and an audio output line. An automatic gain control circuit is coupled between the wire coupler and the audio output line and a filter and line driver are coupled between the audio input line and the wire coupler. A control unit including a microprocessor, a tone encoder, a tone decoder, a timer, a clock, and a memory is coupled by output lines to the automatic gain control circuit for controlling the modes of operation thereof which include a slow decay mode, a fast decay mode, an adapt mode and a hold gain mode. The output from the gain control circuit is also routed through a band pass filter and a limiter to the control unit.

Abstract: A data message transmission system for a cellular radiotelephone system is disclosed. Data to be transmitted is converted into a format compatible with radio transmission prior to transmission. The data is reconverted to its original format following reception. Handoff is accomplished by halting the data transmission prior to handoff and resuming data transmission after handoff. Call supervision occurs via busy-idle bit coding.

Abstract: A decoding system and method is disclosed for a radiotelephone system carrying digital messages. A set of multibit high auto-correlation, low cross-correlation synchronization words and their ones complement inverses are employed for message synchronization and supervisory functions. System state communication is achieved by utilizing a sequence of normal synchronization words and their ones complement inverses. Reliability of the coding is achieved by detecting normal or inverse words as binary levels when fewer than a predetermined number of bit errors exist in the bit sequence. If the predetermined number of bit errors is exceeded, a selected binary one or zero is substituted. This selected sequence of binary levels is decoded and the Hamming distance between a masked decoded sequence and a masked selected sequence is calculated.

Abstract: A communications system for carrying messages via a radio channel between one central site of a plurality of central sites and a plurality of two-way remote data units is disclosed. Each central site has a radio coverage area and each remote unit has a unique address and association with one of the central sites. When a message addressed to one of the remote units is received in a central site, a file of remote unit addresses is searched to find the location and central site association of the remote unit to which the message is addressed. If an address match is found indicating that the remote transceiver is in the coverage area of the message-receiving central site, the addressed message is stored and transmitted in that site. If an address match is found indicating that the remote transceiver is in another central site, the addressed message is conveyed to that site for transmission.

Abstract: A two-way radio communications system of the simplex or half-duplex type having a communication link to a duplex telephone system is provided wherein the simplex or half duplex mobile radio is provided priority to talk upon demand. The communication link is provided without the time delays inherent in conventional systems.

Abstract: A modulatable oscillator for radio frequencies is disclosed in which the single resonant tank includes a tightly coupled varactor diode for wideband modulation and frequency control. Nonlinearities introduced by the varactor diode are compensated by predistortion of the modulated signal yielding a predetermined modulation characteristic which is maintained over temperature.