Abstract: An improved FM companding communication system is disclosed in which noise bursts and pops in the audio output of the receiver, due to weak and Rayleigh-faded signals, are minimized by selectively attenuating the audio signal in the receiver prior to expansion. The amount and rate of attenuation for the noise reduction circuits is determined by a control signal derived from either the average discriminator noise at frequencies above 3 kHz, or from a received RF signal strength indicator, or a combination of both. The audio output is attenuated during weak signals or Rayleigh fades only when the attenuation control signal increases above a predetermined signal-to-noise ratio threshold. Preferably, attenuation increases at a rate greater than the decrease in the received signal strength. The invention includes a circuit for modifying the expansion characteristics of the expandor to minimize signal clipping in the output audio stage of the receiver due to limited dynamic range.

Abstract: A digital interface between at least two subscriber line interface circuits and a processing unit is described. The interface is configured in the form of a parallel interface. The level of an input/output register and of a control register is allocated, as needed, to the connections of the processing unit. These connections can be operated selectively as inputs or outputs. They can also be operated in two modes, depending upon which type of subscriber line interface circuit (SLIC) is connected. The connections of the last-mentioned units are partially operable as inputs or outputs and partially operable only as inputs but in the input case, selectively for various types of input signals.

Abstract: A digital data transfer system for transferring baseband digital data between a central location and a patient's room is provided. The system employs the existing coaxial cable network found in hospitals and other institutions. The coaxial cable carries power from a DC power source to the patient's television receiver or other device. Digital data is addressed and transmitted from the central location to the individual patient's room on the coaxial cable by temporarily disconnecting the DC power source from the coaxial cable for each bit which is to be transferred (source switching) and detecting, in the patient's room, the interruption in the flow of DC current through the cable. Digital data is transmitted from the patient's room back to the central location on the same single coaxial cable by temporarily disconnecting the load, e.g.

Abstract: A transmitter attachment for hunting arrows includes a hollow tubular member which is removably mounted between the arrowhead and shaft of a conventional hunting arrow. The tubular member has a transmitter mounted in one end, and a battery slidably mounted between a pair of spring contacts in the other end. The battery is mounted so as to slide forward into electrical contact with a coil spring, which closes an electrical circuit to energize the transmitter, when the arrow hits the target or the ground. Thus, the combination of battery and contacts forms a type of inertia switch. A directional receiver is utilized to locate the arrow. The transmitter is deactivated by tapping the nock-end of the arrow against the ground--which slides the battery out of contact with the coil spring.

Abstract: Data is transmitted from a mobile or a base station to a booster or repeater station which, if it identifies that the same message has been retransmitted a preset number of times by the mobile or base station it automatically retransmits the data. The number of times a message has been retransmitted may be coded on each message or determined by comparing the retransmitted messages with a previously sent message that will have been stored in memory by the repeater and when the message in memory and retransmitted message are the same, registering another transmission of the message until the preset number is registered and then retransmitting the message preferrably from memory. In another arrangement the relay station receives and stores or otherwise identifies data from the mobile or base and listens for an acknowledgement from the receiving station, if no acknowledgement is received within a preset period of time the message is automatically retransmitted by the relay station.

Abstract: A communication system comprising a plurality of devices interconnected into a loop and each provided with two pairs of sending and receiving terminals for transmitting signals in directions different from each other. Each of the devices is connected to the other devices immediately adjacent thereto on the loop by a pair of transmission channels connected to the two pairs of sending and receiving terminals and each including a sending line and a receiving line. Each device comprises a first arrival preference circuit which disciminates whether a first or second input terminal receives a signal first. Also, a control circuit causes the terminal which receives the first arrived signal to accept that signal while the other terminal is inhibited from accepting any signals. A predetermined one of the terminals is controlled to accept an input signal when input signals arrive at the two terminals simultaneously.

Abstract: For use in a common service area of a plurality of radio base stations, each being preassigned with a radio channel and for transmitting a channel status signal indicative of whether the radio channel is idle or busy, a terminal station (14) comprises a monitoring circuit (37) for cyclically monitoring the channel status signals of the respective base stations to produce an internal signal when the radio channel is found idle for one of the base stations that has a highest priority for the terminal status. Responsive to the internal signal, a control circuit (29) inhibits the cyclic monitoring for other base station or stations. The priority is decided by a measuring circuit (27) for measuring field intensities of the respective channel status signals. When the base stations are three in number, operation of the monitoring circuit is inhibited for the channel status signal of a lowest-priority base station when both radio channels of two other base stations are idle.

Abstract: In a superheterodyne receiver which employs a frequency synthesizer to generate local oscillator (LO) frequencies, there is provided apparatus which determines when an undesirable frequency relation exists, which may produce a condition known as a "tweet", and which adjusts the frequency of the LO signal so as to prevent, reduce or eliminate the tweet.

Abstract: A mobile radio tarnsmission system comprises a plurality of base stations (BS) with corresponding service areas (SA) which together cover a geographical area through which mobile stations (M) can roam. Each base station is connected to a central station (CS) by means of a respective two-way communication link (CL). In order that it can be contacted without all the base stations having to put out a call, each mobile station registers in known manner with the base station in whose service area it is situated, and this is recorded by the control station. When it roams into a new service area this process is repeated. However, in order to preclude frequent re-registrations when the mobile station repeatedly crosses the boundary between two service areas, when it registers with a new base station and hence a new service area it retains its registration with at least one service area with which it is already registered, thereby creating its own customized enlarged registration area.

Abstract: There is disclosed a data transmission system in which data are transmitted among plural stations. The system is capable of transmitting data of different rates of formats. The relationship of different sets of data is indicated by the time interval between the sets, and the interval is selected longer than a predetermined value if the sets of data are mutually irrelevant.

Abstract: A television tuning system includes control apparatus for changing the frequency of a local oscillator signal during a search and a comparator arrangement for determining when an AFT signal traverses first and second threshold values corresponding to first and second frequencies in respective "hump" regions of the AFT signal. The frequency of the local oscillator is set to the average of the first and second frequencies in order to set the frequency of the IF picture carrier closer to the nominal value than the first and second frequencies.

Abstract: A diversity combiner is provided for combining two received radio signals having the same frequency and modulation. For each of the radio signals (s, s') there is included a mixer (1, 1') with an associated voltage controlled local oscillator (2, 2') and a following intermediate frequency filter (3, 3') for generating an intermediate frequency signal (m,m') and a phase comparator (5, 5') for comparing the intermediate frequency signal with a reference signal (a) originating from a weighted aggregate (e) of the intermediate frequency signals (m, m). Each phase comparator (5, 5') sends a signal responsive to the phase difference and which controls the frequency of the local oscillator (2, 2'). The weights of the sub signals can be varied such that the quotient of the contribution of the sub-signals to the aggregate can be caused to correspond to an arbitrary power, which is greater than or equal to one, of a corresponding quotient before the addition.

Abstract: A satellite TV system including a plurality of channel strips each including a tuner and a modulator matched to each other. The tuner selects the particular satellite signal and the modulator selects the particular channel on the TV. Both tuner and modulator circuits include a divide-by-two component which permits use of lower cost electronic components while producing high quality TV pictures or other outputs. Each channel strip is in the form of a plug-in module. A control box houses all of the plug-in channel strips and the other electronics.

Abstract: An improved field programmable matrix circuit. The matrix circuit includes a plurality of pairs of input lines having noninverted and inverted inputs. These input lines intersect a plurality of output column lines. A single transistor is used to provide a programmable connection to each column line from both the inverted and noninverted inputs of an input line pair. The transistor has a source, a drain and a gate with either the source or the drain coupled to a voltage potential and the other of the source or the drain coupled to an output column line. The gate is alternately coupled to a noninverted input, an inverted output, or a second voltage potential. The second voltage potential is coupled when it is desired to hold the transistor in an off state.

Abstract: Disclosed is a wiring system which has a terminal device having an output mini-jack connected to a reception antenna, a booster having input and output mini-jacks, intermediate equipment, e.g., a distributor, a branching filter, and the like, and a cable unit having a coaxial cable at two ends of which mini-plugs are arranged, and in which the terminal device and the intermediate equipment are connected by the cable unit. The cable unit has a small-diameter coaxial cable, e.g., a 1.7C-2V cable.

Abstract: Novel FM receivers are disclosed, which are very compact and simple yet possess high sensitivity. The receivers use novel three-terminal and two-terminal negative admittance networks. In one embodiment, one three-terminal negative admittance network forms a complete FM homodyne receiver. In another embodiment, two three-terminal negative admittance networks are used as the frequency converter and the demodulator and other functions of a super-heterodyne receiver. In still another embodiment, a two-terminal negative admittance network is employed together with a three-terminal negative admittance network to form a complete super-heterodyne FM receiver.

Abstract: A VHF-UHF mixer, which has a balun (14) having a ferrite core (141), a pair of R-C parallel connection circuits (15a) and (15b) connected to output ends of the balun (14), a series connection of two mixing diodes (16a) and (16b) connected across output ends of the R-C parallel connection circuits, and a diplexer (17) consisting of a high pass filter and a low pass filter and connected by its input terminal to center connection point (18) of said series connection of the two mixing diodes, further has a pair of impedance circuits (19a,19b), each being grounded by one ends thereof, consisting of L-C-L series connection circuit, and connected to either input end or output end of the R-C parallel connection circuit.

Abstract: An FM receiver is self tested by connecting a positive feedback network in circuit with a wideband, front end r.f. amplifier of the receiver, so that the amplifier is converted into an oscillator. R.f. and i.f. characteristics of the receiver are determined by comparing the amplitude of an i.f. signal with a predetermined reference value while the amplifier is converted to an oscillator. Noise characteristics of the receiver are determined by comparing the amplitude of an audio frequency signal of the receiver with a predetermined value while the amplifier is converted to an oscillator and the amplifier derives an unmodulated r.f. output. Baseband characteristics of the receiver are determined by varying a reactance in the positive feedback path to impose FM on r.f. oscillations derived by the amplifier and by comparing the amplitude of the output of the audio frequency amplifier with a predetermined value.

Abstract: In an AM broadcast transmitter having a switching amplifier as main modulator (12), an additional modulator (18) is used in the radio frequency circuit in order to achieve a steady 100% modulation at the modulation minima, with the aid of which additional modulator the carrier signal is also modulated at the modulation minima. The LF signal needed for controlling the additional modulator (18) passes through a delay circuit (16) and a correction circuit (17).

Abstract: Directly mixing synchronous receiver having an RF input (1) and a first signal path (S1) which is coupled thereto and which incorporates a first synchronous demodulator (3) and a first low-pass filter (4), and having a carrier regeneration circuit including a first phase-locked loop (Q) incorporating in a loop configuration a first phase detector (5) which is coupled to the RF input (1), a first loop filter (6) and a first voltage-controlled tuning oscillator (8) an output of which is coupled to the first phase detector (5), on the one hand, and to the first synchronous demodulator (3) via a phase shift circuit, on the other hand, for a direct demodulation of an RF reception signal to the frequency baseband. The local mixing carrier required for the direct synchronous demodulation should be accurately in phase or in antiphase with the carrier of a desired RF reception signal to be demodulated.