Abstract: The present invention provides for a communication bus (52) and controller (54) which can control communication in more than one communication mode on a TDM bus by inhibiting or interrupting communication in a first mode during communication in a second mode. The bus (52) includes a allocate channel for controlling the bandwidth allocation of the bus amongst the different communication modes.

Abstract: Disclosed is a Digital Service Unit (DSU) which, in response to a digital signal from a Digital Data System (DDS) network, uses different techniques for different possible DDS services (include DDS-SC, CC64, and basic DDS services) to determine the type of DDS service providing the digital signal services and the line rates for such services. With respect to DDS-SC service, the DSU utilizes the fact that this DDS-SC service provides network defined frames of data to which the DSU tries establish frame synchronization at different line rates. The DSU also resolves the fact the DDS-SC service and CC64 service have the same 72 KBPS line rate by detecting the presence or absence of a control bit. For Basic DDS service, the DSU monitors the received signal for a plurality of possible invalid conditions. For each line rate, an error counter for that line rate is incremented each time an invalid condition is detected.

Abstract: The present invention provides a removable telephone line surge protection circuit (104) for use by an electronic deuce such as a modem (102). The line protection circuit (104) protects the modem (102) against telephone line surges such as those caused by lightning strikes. In one embodiment of the invention, the line protection circuit (104) interfaces with test circuitry which is preferably located within the modem (102) in order to allow the modem (102) to determine if the line protection circuit (104) is still operational while the line surge protection circuit (104) is connected to the modem (102). The present invention also provides for a removable surge protection circuit that is a testable module when connected to an electronic device having automatic module test capability as presented in one aspect of the invention. The surge protection circuit also provides for status indication of its operability in order to allow device users to make a quick determination of whether or not the module is damaged.

Abstract: Improved filter assemblies are provided having a pleated filter medium attached to a support frame utilizing an improved manufacturing method employing a welding process to seal the pleated edges of the filter medium to an inwardly protruding sealing means provided on the frame around the inside perimeter thereof, forming a final filter assembly exhibiting an essentially leak-proof edge seal.

Abstract: A positive pressure demand valve for breathing apparatus incorporates a tubular "balanced piston" valve member for regulating the flow of breathing gas from an inlet to an outlet. A coaxial tension spring acts to bias the valve member open and a lever coupled to a pressure-responsive diaphragm acts to push the valve member closed when a predetermined pressure is attained within the outlet. A combined pressure-relief and bypass valve member enables the operation of the main valve member to be bypassed by porting gas through the center of the main valve seat. A "first breath" mechanism is provided comprising a hooked link which can be pressed in by a button to maintain the main valve member closed and can be released by contact by the diaphragm when a negative pressure is applied to the outlet. The outlet is in the form of a bayonet connector which is locked into a corresponding inlet fitting on the user's mask by means of the same button.

Abstract: A battery assembly (200) includes first and second battery housings (202 and 204), a plurality of battery cells (204), and a flexible circuit having a thermal sensing surface (206) which is located in thermal proximity to battery cells (204). The thermal sensing surface (206) is in thermal proximity to the plurality of battery cells (204) providing for improved thermal sensing of battery assembly (200).

Abstract: A receiver automatic gain control (AGC) circuit includes a first adjustable gain control amplifier (158) which is responsive to a gain control signal (156). The AGC circuit further includes a second adjustable gain control amplifier (114) and a control circuit (116) which receives the gain control signal (156) and provides a modified gain control signal or VCNTRL (152) to the second adjustable control amplifier (114). The control circuit (116) also limits the amount of gain control applied to adjustable gain control amplifiers (114 and 118) when the gain control signal (156) reaches a certain predetermined level. This provides for all further gain reduction to occur at the first adjustable gain control amplifier (158) and thereby reduce the chances for distortion under high input signal conditions.

Abstract: A speaker assembly (100) includes a speaker (202) having at least one speaker terminal (206) and a magnet (204) which generates a magnetic field. The speaker assembly (100) also includes a circuit board (116) having at least one terminal (110). A metal member (106) is coupled to the circuit board (116) and is used to magnetically attach speaker (202) to circuit board (116). Upon speaker (202) being magnetically coupled to circuit board (116), the at least one speaker contact (206) becomes coupled to speaker terminal (110). Thereby, allowing for a quick way of attaching and detaching speaker (202) to and from circuit board (116).

Abstract: A radio telephone for a vehicle is provided having means (3) for switching between a handset mode and a hands-free mode, and control means (4, 7, 8, 9, 10, 11) responsive to said means for switching, said control means controlling the telephone such that in hands-free mode the party speaking at a given time has priority in the conversation while in handset mode the party holding the handset has priority at a given time.

Abstract: A method is provided for a group of radios to establish a talk group in order for the radios to communicate with each other. The method allows for a group of radios (200) to select a talk group which users can communicate with one another, independent of how the radios in the trunked system (600) are grouped at the system-level.

Abstract: A nested digital phase lock loop (DPLL) circuit (400) provides center bit sampling for incoming recovered data (406). Included in the nested DPLL circuit (400) are a narrow bandwidth DPLL (402) and a wide bandwidth DPLL (404) which generate first (410) and second (428) recovered clock signals respectively. Initially the first recovered clock signal (410) is used to clock in the recovered data (406) until the narrowband DPLL (402) is stabilized. Once the narrowband DPLL (402) is stabilized, the second recovered clock signal (428) generated from the wideband DPLL (404) is switched in by a multiplexer (424). If for any reason the center bit sampled data becomes corrupted, a RESET occurs in the wideband loop (404) to zero out the phase shift of the second recovered clock signal (428) to match that of the narrow loop. Thus, when a RESET occurs, the wideband loop is tracking at exactly the same clock rate as the narrowband loop.

Abstract: A multilayer printed circuit board (100) includes a plurality of layers (101, 102, 104, 106, 108 and 110). Located within intermediate layer (106) is an inductor (200) which is shielded by top layer ground plane (202) and bottom layer ground plane (204). In another embodiment of the present invention, the inductor (200) can have its inductance adjusted by way of a inductance adjustment runner (316, 318) or by an electronic inductance adjustment device (408).

Abstract: A DC translation circuit (200) provides maximum dynamic range in DC level shifting that is temperature and process invariant. The DC translation circuit (200) includes a bandgap reference (202) and current mirror circuit (204) for providing a reference current, Iref. An op-amp circuit (210) receives an AC signal centered about a first DC level, and translates the first DC level into a second DC level using the reference current, a current mirror circuit (208), op-amp circuit (210) and resistor (R2).

Abstract: A sizeable attachment device includes a flexible member (102) and a set of first (108) and second (106) sockets which receive a set of back-to back studs formed from back-to-back pairs (110, 112). In a first attachment mode stud 110 is snap fitted to socket 108. In a second attachment mode stud 110 is snap fitted to socket 106, and stud 112 is snap fitted to socket 108. The sizeable attachment device forms two sizes of loops for receiving belts or holsters having different widths. The sizeable attachment device provides for a clean and good looking attachment when either in the first or second attachment modes.

Abstract: A pad arrangement (100) for aligning and attaching a surface mount component (402) with other circuitry includes a substrate (102) upon which opposing pads (108) are attached. Each of the pads occupies a substantially rectangular area (110) having four sides. In order to facilitate alignment of the surface mount component the substantially rectangular area has two opposing flat sides an outwardly extending arcuate area (112) along at least one of the other two sides.

Abstract: A radio transceiver includes a first local oscillator (114) which is preferably a synthesizer providing a first LO signal, and a second local oscillator providing a second LO signal. The radio further includes a first mixer (110) for mixing the received RF signal and the first LO signal to produce a first IF signal having a frequency which is the difference of the two inputs. The first IF signal is then mixed with the second LO signal by a second mixer (124) where a second IF signal is produced which is preferably at zero frequency. During transmission, the radio uses a conventional modulator to modulate the second LO signal which is then mixed with the first LO signal by a transmitter offset mixer (112), where the output is a modulated RF signal.

Abstract: A voltage regulator (200) includes a controller (204) which selectively activates a plurality of switching means (208, 210, 214, and 212) in order to select between a first current loop in which an energy storage device is charged by an input supply and a second loop in which the energy storage device is coupled to the output terminal (242) of the regulator (200). The switching from the second current loop to the first is governed by the controller (204) determining that the loop current in the second loop has reached a predetermined level. A first switching audio amplifier (300) is disclosed which uses the voltage regulator (200) to provide a continuously variable output voltage (318) in order to provide for high quality amplification which is independent of the volume setting. A second audio amplifier (400)includes a converter (436) which provides discrete voltage levels to a full wave bridge in order to provide improved audio output.

Abstract: Pulsewidth-modulated amplifier (100) includes a controller (102) which provides for a set of compensated signals (114, 158 and 160). The compensated signals are used for driving a speaker (136). Controller (100) includes a storage area for storing distortion characteristics for the amplifier for a predetermined operational frequency range. The compensated drive signals (114, 158 and 160) help compensate for the electrical non-linear distortions that occur in amplifier (100) and thereby help reduce the output distortion of amplifier (100).

Abstract: A includes a non-piezoelectric substrate and a piezoelectric substrate (206) having matched transducers on both opposed surfaces of the piezoelectric substrate (206). The matched transducers being 180 degrees out of phase from one another. The present invention provides for improved coupling due to the new SAW the multilayer transducer topology.