Abstract: Belt clip assembly for use with a portable electronic apparatus includes a mounting bracket used to join a belt clip and a housing member. A mounting bracket is inserted through a pair of slots in a housing member and holds a belt clip in place by means of a pivot pin inserted through apertures in the mounting bracket and the belt clip. A pair of shear cuts adjacent the apertures in the mounting bracket allow the pivot pin to pull through the shear cuts in the event excess forces are applied to the belt clip, thereby destroying the mounting bracket. In this manner an inexpensive mounting bracket is sacrificed to avoid damage to the housing and the belt clip.

Abstract: A sealed container having a test port with a membrane which is pervious to gas and impervious to liquid may be tested by connecting a pressure device such as a vacuum pump or pressure pump to the test port and creating a pressure differential between the container side of the membrane and the pump side of the membrane, allowing the pressure differential to equalize through the membrane and monitoring the equalized pressure to detect whether or not the equalized pressure changes, which utilmately allows the observer to determine whether the sealed container has any leaks. If the pressure equalization time is substantially zero, the membrane and/or membrane seal is defective. In the event a leak is determined, the inside of the radio device may be pressurized to a selected pressure, by use of a pressure pump or the like, and then immersed in a liquid such as water. The location of the leak may then be detected by observing the emanation of air bubbles from that portion of the device in which the leak exists.

Abstract: An improved header and housing assembly for holding a miniaturized electronic circuit module having a plurality of leads includes a header member having a plurality of apertures arranged to accept the leads of the module. A jaw mechanism associated with each aperture captivates the leads and a protective housing encloses the module between the header member and the housing. An interconnection board which is mounted to a flexible printed circuit board engages the header and housing assembly and forms a base permitting the assembly to be mounted to the flexible circuit board.

Abstract: Piezoelectric filter includes a piezoelectric substrate having an upper and lower opposed major surfaces. A plurality of N coupled resonators where N is an integer greater than two exposed on the surface of the substrate. A plurality of mounting pedestals are utilized to couple the resonators to ground in a manner such that no two non-adjacent resonators are coupled to any one pedestal. This mounting scheme suppresses undesired spurious attenuation poles and improves the selectivity of the piezoelectric filter.

Abstract: A paging device and supporting receptacle are provided for detachably securing the device to an article of clothing and providing for limited pivotal movement of the device to permit visual observation of a display portion of the device without completely removing the device from the receptacle.

Abstract: A diversity signal strength indicator for transmission site selection in a cellular-like mobile radio system produces an output strength indication signal which is proportional to the logarithm of the average strength of two diversity input signals. The two input diversity signals are time multiplexed together to form a composite signal, and a log amplifier/envelope detector then produces an intermediate log signal which is proportional to the logarithm of the envelope of the composite signal. The intermediate log signal is then operated on by a peak detector to produce a peak intermediate log signal which is then passed through a low pass filter to produce an output strength detection signal proportional to the average of the intermediate log signal and thus proportional to the logarithm of the average strength of the diversity input signal.

Abstract: An MOS crystal controlled oscillator circuit is provided which includes a pair of MOS transistors coupled together in complementary fashion to form a first non-inverting stage. The output of the first non-inverting stage is coupled to the input of a second non-inverting stage including a MOS transistor exhibiting a source follower configuration or a bipolar transistor exhibiting an emitter follower configuration. The output of the second non-inverting source follower stage is coupled via a feedback element, for example, a piezoelectric crystal, to the input of the first non-inverting stage. A feedback loop is thus formed which causes the circuit to resonate at a frequency determined by the piezoelectric crystal feedback device. This oscillator configuration results in a degree of insensitivity to variations in parasitic impedance of the piezoelectric crystal feedback device.

Abstract: This invention is directed to an AT-cut quartz resonator having two different resonant modes simultaneously occurring in which a generally rectangular polyhedron has first and second electrodes disposed on opposing faces, and having the width to height selected within the range of 8 to 25. The width is selected such that a thickness shear mode and flexure mode are simultaneously excitable and coupled together. The AT rotation angle is selected so that a first signal responsive to the coupled flexure mode and thickness shear mode has a substantially cubic frequency versus temperature response over a desired temperature range and a second signal responsive to the coupled flexure and thickness shear modes has a substantially linear frequency versus temperature response over the desired temperature range.

Abstract: A single carrier is amplitude-modulated by a signal which is a transform (as the sine function) of the audio signal, and one set of sidebands is removed. In a receiver, the signal can be recovered by first deriving the Hilbert transform of the sine transform, and multiplying it by the signum of the derivative of the original audio signal to obtain the cosine transform. The sine and cosine transforms are then decoded to obtain the original audio signal.

Abstract: A current mirror circuit comprising a first current mirror circuit with a first error correction transistor connected between the base and collector of the first transistor of the first current mirror; a second error correction transistor connected to the first error correction transistor and a second current mirror circuit connected to an input current source and the base of the second error correction transistor. The second error correction transistor samples the signal from the collector of first error correction transistor and feeds its base current, which is almost equivalent to the base current of the first error correction transistor, to the input of the second current mirror circuit. The second current mirror circuit combines the input current source current with the base current of the second error correction transistor and generates a current which is fed to the collector of the first transistor of the first current mirror circuit.

Abstract: A low-profile crystal package wherein the wire bonding operation from the electrode pattern of the crystal plate to the terminal posts may be accomplished without fear of fracture of the crystal plate itself. The crystal blank is positioned on a support member which in turn initially sits on a ring of indium. In this position, the crystal blank is not in contact with the split center support post whose top surface is covered with indium paste, and is supported around its periphery during wire bonding. When all the wire bonding operations are effectuated, the assembly is subjected to sufficient heat wherein the indium material will melt, which will cause the support member to be drawn downward, thereby resulting in the crystal plate being supported and fastened only by the center supports, with the periphery of the crystal plate being free to vibrate with no extraneous dampened support.

Abstract: A data communications system is described that covers a geographic area divided into a plurality of non-overlapping zones and includes a general communications controller (GCC), a plurality of channel communications modules (CCM) and associated transmitters and receivers, and a plurality of portable radios. Message signals carrying alphanumeric information are communicated between the GCC and the portable radios by way of a radio channel. Each CCM takes a signal strength measurement every time it receives a message signal from a portable radio. The GCC gathers the signal strength measurements from the CCM receivers receiving the same message signal and computes an adjusted signal strength for each zone. The GCC then selects the zone having the largest adjusted signal strength for determining the location of the portable radio that transmitted the message signal.

Abstract: A radio paging device is provided which includes apparatus for preventing turn off of the paging device until all selective calling message signals which are stored in the pagers memory have been displayed. The pager of the present invention further includes apparatus for automatically initiating interrogation of the memory when the user attempts to turn off the paging device.

Abstract: Improved control circuitry for pulse-width-modulated power supplies is described that includes a pulse generator for generating a train of trigger pulses at a predetermined repetition frequency, a signal source for generating a reference voltage and a comparator for comparing the power supply output voltage to the reference voltage and generating a first state of a switching control signal in response to each trigger pulse from the pulse generator and a second state of the switching control signal when the magnitude of the power supply output voltage is equal to the magnitude of the reference voltage. The first state of the switching control signal enables switching transistors of the switching power supply, and the second state of the switching control signal disables the switching transistors. The comparator also includes circuitry for reducing the magnitude of the reference voltage when the switching control signal has the second state.

Abstract: A data communications system is described in which variable length messages are communicated between a general communications controller (GCC) and a plurality of portable and mobile radios. The variable length messages include a bit synchronization field, a message synchronization field and a plurality of channel data blocks for efficiently and reliably handling long strings of data or text. Each channel data block includes an information field, a parity field for error-connecting the information field and a channel state field indicating whether or not the radio channel is busy or free. The GCC is coupled to a cellular arrangement of channel communications modules (CCM's), which each include a radio transmitter and/or radio receiver. The mobile and portable radios communicate with the GCC by way of the CCM's.