Abstract: In a communications system wherein a transmitted message is preceeded only by an address, an asynchronous circuit detects the address and provides an initializing signal to a synchronous clock recovery circuit so that the first bit of the recovered clock signal is synchronized to the first bit of the message. During the transmission of the message the synchronous clock recovery circuit makes minor adjustments to the phase of the recovered clock to maintain synchronization between the recovered clock and the message. At the termination of the message, the synchronous clock recovery circuit is inhibited until the asynchronous circuit detects another address.

Abstract: In a battery powered radio paging receiver, a battery saving method extends battery life and prevents the loss of messages stored in volatile random access memory. Upon receipt of a message, a plurality of alerting devices (vibrators, LCD back-lights, LED's and audio alert tone generators) are sequentially activated. Before each device is activated, however, the battery voltage is checked to determine if sufficient charge remains to power the alerting device without dropping the battery voltage below the minimum requirement for retaining information in the memory. If an alerting device is activated, the battery voltage is repeatedly checked and if it drops below a threshold level, the device is deactivated. If the alerting device is an escalating volume audio alert tone generator and the battery voltage is below a threshold voltage, the volume of the generator is restricted to its lower volume range. The received message is also checked to determine if it has a priority status.

Abstract: A display device has a single switch that transfers a stored message to a liquid crystal display and simultaneously activates a supplemental display lighting system. The supplemental lighting system is inhibited, however, when circuitry senses that ambient light conditions are sufficient to illuminate the display.

Abstract: An electrical interconnect pin, particularly suitable for attachment to the edge of a flexible printed circuit board or "flex circuit", has an edge clip with an opening that can be temporarily enlarged to facilitate the attachment of the pin to the edge of a circuit board. The pin includes an elongated shank with a rectangular cross section and two substantially identical clips attached to opposite sides of the shank. To attach the pin to a printed circuit board, the pin is placed on a flat surface with the shank parallel to the surface. A force is then applied to the shank just below the clips and perpendicular to the surface. This force opens up the edge clip and the edge of the printed circuit board is then inserted into the opening of the edge clip. After the force is removed, the edge clip clamps down on the circuit board, temporarily attaching the pin to the board. The pins can then be permanently affixed to the board by soldering.

Abstract: For proper pre-assembly alignment of the hinge plate holes (e.g., 120b and 136b), stops (e.g., 140a) are engaged in notches (e.g., 119b). A hinge pin (128) is then inserted into the aligned holes to attach the clip (130) to the base plate (102). The pin is locked in position by a spring finger (204) that forcibly engages the semicircular wall (202) of one hinge plate hole (120a) into a groove (304) on the pin. A coil spring (122) is unloaded during assembly because its free ends (124a and 124b) project through apertures (116a and 116b) in the base plate. After assembly, the spring is pre-loaded by engaging its free ends under tabs (116a and 116b) that project into the apertures. The base plate has a "U" shaped bracket (502) at one end and a tab (112) on a torsion bar (110) at the other end to attach the assembly to a radio housing.

Abstract: A speech amplifier circuit increases the maximum perceived loudness at the speaker (412) and reduces distortion at high volume levels without increasing the power consumed by the speech powder amplifier (410). When a low volume is selected by the volume control (414), the microcomputer (418) sets the step attenuator (406) at a correspondingly high attenuation level and the high-pass filter (408) is bypassed. As the volume control (414) is advanced and the speech power amplifier (410) is 12 dB into clipping, the microcomputer (418) activates the high-pass filter (408) and simultaneously steps the gain of the step attenuator (406) by 6 dB.

Abstract: An expandable chassis includes a four sided frame with a central opening to receive a plate or "shield" which is allowed to move within the frame between two predetermined positions. Protuberances on the shield contact the frame and limit its inward movement while outward movement is limited by a spring clip on the shield that snaps into an aperture in the frame. Tabs on the frame support integrally formed spring fingers on the shield which tend to force the shield outward. A membrane switch contact assembly and a speaker are respectively attached to the inside and outside surfaces of the shield. By compressing the shield partially into the frame, the chassis assembly slides into a molded plastic housing. A rubber key actuator pad on the outside of the housing has a plurality of keys each having a protrusion or "actuator" that extends partially into an actuator hole in the housing. When the key is depressed, the actuator depresses and activates one of the switches in the membrane switch contact assembly.

Abstract: A controller module includes a cast module base having a central recess with a peripheral ledge. A cover plate is positioned in the recess and supported by the ledge. A flexible circuit is attached to the inside surface of the cover plate and includes two integral flexible circuit connectors. One connector protrudes through an opening in the side of the module base while the second connector wraps around an edge of the cover plate and is adhesively bonded to the outside surface of the cover plate. The flexible circuit includes a polyimide substrate with electrical circuit patterns disposed on opposite sides of the substrate. A polyimide cover layer is adhesively bonded over one electrical circuit pattern and the cover layer is then adhesively bonded to the inside surface of the cover plate. A solder resist layer is applied over portions of the other electrical circuit pattern leaving exposed areas for soldering and electrical contact.

Abstract: A clear plastic lens contains a fluorescent dye. The lens is substantially parallelepiped in shape with two major opposed parallel surfaces and four sides. Three of the sides are reflecting sides. Each reflecting side has two flat transparent surfaces positioned at angles of 135 degrees relative to the opposed parallel surfaces. The fourth side is a transmitting side that has one flat transparent surface perpendicular to the opposed parallel surfaces. Light enters the lens through an opposed parallel surface, is absorbed by the fluorescent dye, and is emitted a short time later. The emitted light is reflected at the reflecting sides and opposed surfaces, and redirected towards the transmitting side where it passes into the environment as a collimated beam.In another embodiment, the transmitting side is at an oblique angle relative to the opposed parallel surfaces and has a plurality of small steps. Each step has two surfaces, one perpendicular and one parallel to the opposed parallel surfaces.

Abstract: An electrically variable three terminal monomorphic piezoelectric capacitor is manufactured with thick or thin film hybrid microelectronic circuit technology. A first capacitor plate and a ridge, which substantially surrounds and extends above the first capacitor plate, are formed on the surface of a substrate. A monomorphic piezoelectric wafer having a control plate and a second capacitor plate on opposing surfaces is bonded to the upper surface of the ridge. During bonding, a force is applied at the center of the wafer which fixes a permanent bow in the wafer in the direction of the first capacitor plate. A four terminal monomorphic embodiment and three and four terminal bimorphic embodiments are also described.

Abstract: A liquid crystal display module with self contained display decoder circuitry is attached to a radio frame with a minimum of electrical interconnections. Module assembly and attachment are both accomplished without the use of tools. Attaching the module to the frame interlocks the module to prevent accidental disassembly and places a preload force on the electrical interconnections to insure good electrical continuity. Ambient light reflection provides primary display illumination while lamps, controlled by an integral switch, provide secondary illumination.

Abstract: An R.F. switch includes a directional coupler with a main line and a quarter wavelength coupled arm. One end of the main line is connected to a first input port and the other end is connected to a first output port. The coupled arm is selectibly terminated at one end in either its characteristic impedance or a short. A PIN diode controls the termination. The second end of the coupled arm is connected to a second input port. A PIN diode switch is connected between the second end of the coupled arm and a second output port. In a first position, signals present at the input ports are combined and appear at the first output port. The directional coupler provides isolation such that the signal at the second input port is not coupled to the first input port. In the second position, the signal at the second input port is disconnected from the first output port and only connected to the second output port.

Abstract: An I.sup.2 L programmable read only memory (PROM) row driver circuit sinks current from a row of memory elements when selectively activated. The circuit operates in the read mode at very low power levels and down to 1.0 volt. The circuit has two current sinking capabilities, a low current capability for the read mode and a high current capability for the program mode. Switching between modes is accomplished merely by changing the voltage on a power supply terminal; 1-3 volts for the read mode and 9-12 volts for program.

Abstract: An RF interconnect between a printed circuit board and a coaxial connector mounted in a housing is self-aligning along all three major axes. The coaxial connector has a pin connected to its inner conductor that extends beyond the edge of the outer conductor. The outer conductor has an external circumferential groove. The interconnect includes two terminals wherein the first terminal includes a substantially "M" shaped wire formed conductor having five functional segments: two flexible attaching segments near the ends of the wire, two substantially parallel pin contact segments, and a joining segment connecting the pin contact segments. The coaxial connector pin is inserted between the parallel pin contact segments of the wire formed conductor and a clamping force is generated on the pin by the joining segment. The second terminal includes a flat flexible conductor that has a "U" shaped lug at one end and a snap ring at the other end which is inserted into the groove of the coaxial connector.

Abstract: A portable radio housing has a shield that provides electromagnetic isolation between logic and radio boards operating on close frequencies. The radio board is positioned in a conductive frame having fours sides surrounding a central opening. A tab on the frame is connected to a power module on the radio board to sink heat from the power module. A middle shield having sides with integral spring fingers at calculated intervals is attached to the frame over the rear surface of the radio board. A logic board and rear shield are attached to the frame over the middle shield. A connector protrudes through an opening in the middle shield and interconnects the logic and radio boards. A front shield, also having sides with integral spring fingers, is attached to the frame over the front surface of the radio board. The front shield has an integral speaker baffle and tabs for holding a connector. An outer housing and keypad/display module enclose the frame.

Abstract: An electrically variable three terminal monomorphic piezoelectric capacitor is manufactured with thick or thin film hybrid microelectronic circuit technology. A first capacitor plate and a ridge, which substantially surrounds and extends above the first capacitor plate, are formed on the surface of a substrate. A monomorphic piezoelectric wafer having a control plate and a second capacitor plate on opposing surfaces is bonded to the upper surface of the ridge. During bonding, a force is applied at the center of the wafer which fixes a permanent bow in the wafer in the direction of the first capacitor plate. A four terminal monomorphic embodiment and three and four terminal bimorphic embodiments are also described.

Abstract: A flexible printed circuit board assembly having an integrated circuit die bonded directly thereto. A first layer of the flexible printed circuit board assembly includes a plurality of conductive paths and geometrical patterns on each of its surfaces. The conductive patterns include pads for mounting the integrated circuit die and connecting the wires from the integrated circuit. Additional intermediate layers of the flexible printed circuit board assembly, having an aggregate thickness greater than the height of the integrated circuit die and associated leads bonded thereto, surround the integrated circuit die. The top layer of the flexible printed circuit board provides for total encapsulation of the integrated circuit die for protection thereof. In the preferred embodiment that portion of the top layer which covers the integrated circuit die is opaque to prevent the passage of ultraviolet light which might otherwise cause damage to the integrated circuit.

Abstract: An LED and battery powered driver circuit provide efficient operation to conserve battery energy and maintain the intensity of light emitted from the LED at a substantially constant level despite changes in the battery voltage due to charging and discharging. A pulsed voltage output of a switching power supply is capacitively coupled to the LED. The voltage amplitude of the output pulses is maintained substantially constant by a duty cycle modulator which is connected in a feedback path of the switching power supply. A diode or a transistor circuit is provided to discharge the capacitor between voltage pulses.