Abstract: A demodulator of the type employed in a "zero-IF" system uses a local oscillator for providing quadrature output signals at the center frequency of a received signal to be demodulated. The demodulator has first and second mixers for separately mixing the received signal with the quadrature signals to provide a first and second output signal each in quadrature at the outputs of said mixers. These signals are low pass filtered. The demodulator includes third and fourth mixers with each mixer respectively receiving at an input one of the first and second low pass signals. At another input the mixers receive third and fourth signals. The third and fourth signals are derived from mixing a variable controlled oscillator (VCO) signal with local oscillator quadrature signals the frequency of said is independent of the center frequency of the received signal.

Abstract: Prism couplers are manufactured by disposing a prism (10) on an optically flat waveguide (11) such that the region therebetween is shaped for substantially optimum coupling of optical energy therebetween, and securing the prism to the waveguide without deformation of the waveguide. The prism may have a curved, for example part-cylindrical, base (FIG. 4) or be separated from the waveguide by appropriate spacers (FIGS. 5 or 6). The prism may be secured to the wavegudie by an optical epoxy compound.

Abstract: The locating function of a cellular mobile radio telephone system is implemented so that, when the locating radio detects a sustained change from a very low signal quality or amplitude (indicating background noise rather than an active call in an adjacent cell) to a higher quality or amplitude (indicating the start of a call in one of the adjacent cells), the radio will modify its filtering process so that previous sample values (which can be attributed, for example, to noise before the start of the call) will not be used in the averaging process. The result of this improvement is that values reported from the locating radio during the initial portion of the call (0 to 20 seconds) will not be reported artifically low. This allows the system to make decisions about handoff during this initial portion of the call. Additionally, rather than having the locating radio take equal samples from each of the possible voice channels, in accordance with the invention, there are two scanning tasks.

Abstract: A frequency hopping data communication system for a bidirectional communication system is described in which improved operation in a jamming and/or fading environment is provided. A pseudo-noise code generator is utilized to provide a random sequence of ON-OFF pulses representative of binary numbers which cause a microprocessor to select data at a desired frequency which is then coupled to a frequency synthesizer to provide a controllable frequency and an improved anti-jam capability in both a receiver and transmitter.

Abstract: A telephone subset with a desk and wall mount capability employs an east-to-west oriented handset. The subset base has a bearing at a first axis on which the subset housing pivots. The base has slots for the tabs of a bracket to engage and hold the subset in the desk or wall positions. The housing provides a cylindrical well in which a spring loaded pin is mounted, and also provides surfaces on which the subset handset cradle, which houses the hookswitch, rests in the desk and wall configurations. To prevent the bracket from translating, the spring loaded pin engages a hole in the bracket. As the pin is depressed, it disengages the hole and allows the smaller diameter section of the pin to enter the slot so the bracket can translate. The bracket provides an axle on which the cradle mounts, forming a pivot at a second axis, for pivoting from a desk position to a wall position.

Abstract: A voice-controlled hands-free facility contains a microphone, an internal and an external loudspeaker, and two series combinations of an input amplifier (EV), a variable attenuator (DR), and an output amplifier (AV), one for the send path and one for the receive path, and is controlled by a voice control unit (SS) connected to the output (E) of the input amplifier (EV), to the output (D) of the variable attenuator (DR), and, by a line (L), to an input of the variable attenuator (DR).To permit the hands-free facility to be switched from a single-part mode of operation to a two-part mode, the output (E) of the input amplifier (EV) in the send path and/or the receive path is connected to the output (A) of the output amplifiers (AV) through a bypass device (BP) and a switching unit (T).

Abstract: In the novel equipment for the stereophonic sound reproduction in the television receiver all essential components, such as loudspeakers, crossover networks, etc., are accommodated in one single enclosure which fits into the space above the picture tube, in which it is mounted.

Abstract: In the standard DME system, an airborne station having transmitted a pair of interrogation pulses receives a plurality of pairs of space-coded reply pulses from which the pulse pairs intended for the airborne station are selected by a decoder (DK) and a correlator (KR).The invention uses the first pulse of the selected pulse pair for the distance measurement. A measuring counter (MZ) is provided whose count is transferred to a register file (SR) at the reception of every pulse. A reply signal intended for the airborne station stops the write operation, it being insured that the counts based on the two pulses of the reply signal intended for the airborne station are contained in the register file (SR). Starting from the last count based on the second pulse, an evaluating circuit calculates back to the first pulse, taking account of the decoded pulse spacing.

Abstract: The mobile radio set has a rectangular parallelepiped-shaped case suitable for mounting in the dashboard of an automobile. The handset can be locked at its earpiece and mouthpiece into a cradle mounted on the front panel of the case so that the handset can be positioned in a rest position across the front panel. The keys, mounted on the side of the handset facing away from the cradle, are readable and operable in the rest position of the handset. With a lock mounted in the handset, the mobile radio set can be deenergized and the handset can be blocked in the cradle.

Abstract: A volume control device suitable for installation on the ringer of a telephone incorporates a tone control lever having a damping element cantilevered therefrom and extending as a wing from a point of pivoting in a direction generally parallel to a frame of the ringer. The lever further comprises an arm bent through the frame to serve as a handle, and a leg extending in an opposite direction from the pivot for contacting a detent structure integrally formed with the frame. Also, integrally formed with the frame, are a ramp and a guide. The guide extends upwardly from the frame and then over a path of travel of an outer end of the wing for urging the wing downward so as to ensure passage of the wing underneath a rim of the gong during a rotation of the lever about the pivot.

Abstract: An optical receiver which consists of an optical attenuator, an optical-to-electrical transducer, an amplifier, and an automatic level control circuit. The optical attenuator is an electrooptical modulator which is electrically controlled by the automatic level control circuit.

Abstract: In a loudspeaking telephone the power supply to the loudspeaker amplifier is shunted by a regulator which functions as a programmable Zener diode. Under conditions of low available line current, e.g. where two similar instruments are operated in parallel at the end of a long line, the regulator voltage is reduced in value to disable the amplifier and conserve power to maintain the basic operating functions of the telephone.

Abstract: In a push-button switch, the switch element is a cantilever (2) of thin silicon strain gauge material with a small magnet (1), e.g. of samarium cobalt alloy at its free end. Adjacent to the free end there is an annular magnet (3), e.g. of plastics material impregnated with samarium cobalt alloy, on the push rod (4) of the switch. The annular magnet (3) is so poled that movement of the rod (4) causes, due to magnetic forces, the deflection of the silicon strain gauge to give an electrical output.The return force, plus collapse action, is provided by a soft iron collar (5) on the switch structure.

Abstract: A transmission chip for a telephone subscriber's instrument can be used in a variety of modes, some of which involve use with other chips. Depending on which mode is in force, different amplifiers are used. Thus for plain ordinary telephone (POT) service, amplifiers 30,35 and 43 are used, for loudspeaking mode amplifiers 30, 35 and 43 are used, for handsfree use amplifiers 35, 43 and 46 are used, while for VF "dialling" amplifier 46 is used. To save power, the control block (42) detects the mode in which the set is operating and, via a control bus, operates electronic switches to disable the amplifiers not needed.

Abstract: The digital tie line provides a high speed pulse code modulation (PCM) digital path between private branch exchange (PBX) systems. The invention has a capability of providing a plurality of simultaneous two-way channels. By providing for twice the number of available channels in each PBX system, PBX systems may be interconnected by using one digital tie line per system, resulting in a non-blocking traffic situation between systems. High speed digital data may be directly passed via assigned channels between systems. The digital tie line provides a connection between the internal system parallel PCM bus and an externally located serial bus. A multiple PBX network can be interconnected by multiple external buses by employing a single digital tie line in each PBX system, per external bus. A modular time slot interchanger (MTSI) is used to direct signals between the system PCM bus and the external bus.

Abstract: There is disclosed a multiple processor system which employs dynamically programmable processing elements (DDPE) utilized as slave devices and under the control of a master processor. A plurality of DPPE's have input/output data lines connected to a digital signal processing (DSP) bus. Communication between the DPPE's is afforded via the (DSP) bus from a master processor which interfaces with the bus via a dual port memory designated as a global memory. Each DPPE is connected together via another bidirectional serial bus so that the individual DPPE's can communicate one with the other in regard to processing and exchanging of arithmetic data. The digital signal processing bus allows the master processor to interface with the DPPE devices for control of input/output and control functions. In this manner, the master processor interfaces directly with a codec and has outputs which allow the transmission of plaintext or ciphertext data which data is formed by arithmetic operations performed by the slave DPPE's.