Abstract: An improved amplifier with controlled hysteresis and an extremely low current drain capable of operating over a sufficiently large input voltage dynamic range is provided. Two circuits comprising a transistor and a diode are coupled between a differential amplifier and two cross-coupled current mirrors for preventing transistor saturation in the current mirrors.

Abstract: A system for transmitting long text messages includes a plurality of transmission cells defining different geographical areas, each having a transmitter for simulcast address transmission at a first data bit rate and for transmitting the address and a message at a second data bit rate higher than the first data bit rate. A paging transceiver generates and transmits an acknowledgment signal in response to receiving a transmitted address at the first data bit rate. Receivers located within each of the transmission cells receive the transmitted acknowledgment signal. An apparatus responsive to the received acknowledgment signal identifies the transmission cell in which the paging transceiver is located effecting the selection of the transmitter in the transmission cell in which the paging transceiver is located to transmit the address and message at the second data bit rate higher than the first data bit rate.

Abstract: A multiple frequency message system includes a transmitter for transmitting coded message signals on a plurality of channels of which at least one channel to be assigned to each of a plurality of geographical areas. The coded message signals include channel identification information and message information being transmitted in a sequence of coded transmission slots on each of the plurality of channels. The sequence of coded transmission slots are transmitted offset in time such that a particular transmission slot is not simultaneously transmitted on any of the plurality of channels in each geographical area.A receiver capable of receiving the coded message signals during a predetermined coded transmission slot being transmitted on the plurality of channels is also provided.

Abstract: A ceramic filter including a plurality of ceramic plates contacted by metal plates and enclosed within a housing includes a Teflon membrane having a plurality of bubbles or dimples therein. A curved spring plate is positioned between a wall of the housing and one of the metal plates. The shock absorbing membrane is positioned between the spring plate and the wall of the housing, and the bubbles thereof extend through openings in the spring plate. When the filter is subjected to a force substantially perpendicular to the ceramic plates, the bubbles in the shock absorber cause the edges of the metal plate to deflect upwards and thus support the adjacent ceramic plate so as to avoid shattering or cracking.

Abstract: A battery contact (1) for connecting a battery (9) to an electric circuit (4) is comprised a first portion (2) for coupling to the electric circuit and a second portion (3) for coupling to the battery. The contact is made in one piece of electrically conductive sheet metal and is cut and bent so as to form the second portion into a tapered helical spring. The first portion (2) is formed with two retaining prongs (6,7) which facilitate locating and fixing the contact to the electric circuit (4) and a tab 8 which is used for soldering the contact to the electric circuit. In order to allow the contact to be easily picked-up in an automatic manufacturing line, a flat handling portion (11) is provided between the first and second portions.

Abstract: A hollow tube (3) supports a spring (5) coaxially positioned within the tube (3) and free to rotate within it. The tube (3) has a longitudinal slot (4) through which components (2) threaded onto the coils of the spring (5) hang down. A motor 6 rotates the spring (5) causing the components, constrained by the slot (4), to move longitudinally along the slot (4). When they reach the end of the slot (4), they are orientated by the end of the spring (5), which has been suitably shaped, to the correct orientation to be presented for automatic mounting on a printed circuit board.

Abstract: A protective cover for pagers comprises a film of transparent stretchable plastic (e.g. 595HC silicon plastic) formed to cover the top, four sides, and at least a portion of the bottom of a pager. The cover includes accordion type pleats which are positioned to reside adjacent switches, a belt clip, and the like, to allow operation thereof.

Abstract: An apparatus for generating a remote alert signal in a communication receiver, the apparatus includes a remote alerting device, a latching receptacle enclosed within a casing of the receiver, and an electrical connector cable. The latching receptacle includes a socket accessible from outside the casing and a locking means comprised of a resilient means and an actuating means. The connector cable terminates at one end with the alerting device and at the other end with an electrical connector in the form of a mating plug having a groove extending around the periphery of the plug. The mating plug inserts into the socket and the resilient means being normally biased into the groove prevents disengagement of the mating plug. To release the plug, the actuating means forces the resilient means out of said groove to permit the mating plug to separate from the socket. The connector cable provides electrical communication between the receiver and the alert device.

Abstract: A microcomputer having predetermined clock pulse frequency requirements receives pulses from a multiplying type frequency synthesizer which utilizes a reference frequency less than the largest of the predetermined requirements. The synthesizer is responsive to program instructions to generate clock pulse frequencies sufficient to satisfy the requirement for immediate execution of programmed tasks. As the requirements change, the synthesizer responds to provide only the frequency required. Thus, the power dissipated by the microcomputer system is minimized.

Abstract: A battery housing (4) for a radio pager (1) comprises a slidable cover (5) movable between a first position, where it closes off an opening (3) for insertion and removal of a battery, and a second position where it leaves the opening accessible. The cover (5) is only allowed to move from its closed position when a slidable locking member (8) is moved to its unlocked position. Movement of the cover (5) from its closed position to its open position automatically causes the locking member (8) to be moved back to its locked position so that when the cover (5) is closed again it is automatically locked in the closed position.

Abstract: A solvent soluble plastic form (104) is molded around a spring-type battery contact (102) such that one end (102A) of the battery contact projects from the form. A one-piece injection molded thermoplastic housing (202) is then molded around the battery contact and form, thereby molding the end of the battery contact into the housing. The soluble plastic form is then dissolved in an appropriate solvent, leaving a housing with a cavity (202D) that contains the battery contact.

Abstract: A data limiter in a paging receiver for converting an analog signal to a digital signal, the data limiter having a variable time constant. The data limiter includes an amplifying circuit and an integrating circuit. The amplifying circuit, being responsive to the analog input signal generated from a receiving circuit of the paging receiver, generates a reference signal depending upon a variable bias current input to the amplifying circuit. The integrating circuit, being responsive to the reference signal, generates a comparison signal depending upon a variable gain input. The amplifying circuit responsive to the comparison signal compares the comparison signal to the input signal for generating a digital output signal. A processing circuit of the paging receiver generates a first control signal for modifying the variable bias current input and a second output signal for modifying the variable gain input.

Abstract: A carry case for a portable hand held appliance such as a radio unit is disclosed which is constructed of a soft resilient shock absorbing material and includes a retainer bracket of semirigid material affixed to the interior back wall of the case. This bracket includes a self locating means for centering the portable appliance within the case and a latch means spring biased to locate and retain the portable appliance within the carry case. The radio may be removed by a user's hand contacting an upwardly extending flange to clear the latch means and permit the radio to be removed from the case.

Abstract: A zener diode random number generator circuit is described which produces a random binary number output having a statistical distribution exhibiting a controlled degree of randomness determined in response to an input control signal. A microprocessor feedback circuit monitors the random number output and produces the input control signal in response to the difference between the degree of randomness of the output signal and that of a pre-determined statistical distribution. The digital feedback automatically adjusts the zener diode biasing point and the limiter threshold such that part-to-part tolerance, component aging, temperature variations, or voltage fluctuations will not adversely affect the randomness of the bit stream output. In the preferred embodiment, the microprocessor tests the ratio of ONES bits to ZERO bits of the random number such that a desired 1:1 ONES/ZERO ratio is approximated.

Abstract: A method and means for reducing multipath interference distortion in a time-division multiple access (TDMA) communications system is disclosed. A transmitting station (100) formats one or more equalizer synchronization words with a first user's data word, time-multiplexes this formatted user message with at least one other user message, and transmits the combined signal. The receiving station (200) receives the transmitted TDMA signal, de-multiplexes the first user message from the other user messages, and equalizes the time delay spread characteristics of the data word portion of the first user message (or a stored version of such) in response to this de-multiplexing. Performing the adaptive equalization process more than once per user time slot provides an even higher data throughout for the system. Storing the first user message in a data buffer permits the adaptive equalization process to be performed in non-real time, thereby lowering the required signal processing data rate in any particular receiver.

Abstract: Method and apparatus are disclosed for printed circuit board assembly wherein optimal placement of components are effected. Components, such as microminiature components, are placed, at least on the underside of the circuit board, whereby specially contoured solder pads effect a self-alignment of such components prior to their being affixed in place by a suitable adhesive material.

Abstract: A low-profile antenna for operating in the 800 to 900 mHz range and especially suited for use with portable, hand-held electronic apparatus. The antenna features printed circuit board construction for precision fabrication, broadband operations and enhanced efficiency. The antenna includes a driven element in close association with a parasitic element printed on one surface of the printed circuit board in a side-by-side, parallel relation. A conductive strip is included on the other side of the board spanning the free ends of the driven and parasitic elements to enhance the coupling therebetween.