Abstract: This invention is a technique for providing isolation between the two channels of a handsfree telephone subset without resorting to gain switching or gain variations in the transmission path. The invention involves separating the frequency spectrum into two portions and allowing the stronger signal to capture a major portion of that available spectrum. Switched capacitor filters are used to control the degree of frequency bandwidth allocated to each channel while the filters are clocked from a common source assuring no possibility of overlap in the frequency spectrum. The affect of varying the bandwidth is much less noticeable than varying the amplitude and, therefore, creates much less user irritation.

Abstract: In a local area network (LAN), of the Ethernet type, one of the segments, i.e. one bus, is replaced by a star coupler connected via optical fibre pairs to a number of stations. Each pair includes a GO fibre and a RETURN fibre. As in the usual Ethernet system, collision detection relies on measuring signal level on the medium, if it is too large then a collision condition exists.In an optical fibre system a similar collision detection technique is used. To detect collision, it is nescessary to be aware of the network's attenuation as "seen" by the station. To do this a low level pilot tone is sent from each station, each station having its own tone frequency. The amplitude of this tone when it returns to its own station indicates the system's attenuation, and this is used to detect collision.In an alternative the pilot signals are pseudo-random bit sequences.

Abstract: The invention relates to a method of transferring information between microcomputers in a decentralized process control system, particularly for telephone systems. To prevent contention for possession of the information transfer bus without the need for central equipment, a simple bus system consisting of a multiwire data bus and two single-wire control buses is proposed. Bus mastership is passed on after transmission, with the address of the next transmitter being determined by each microcomputer itself and forming part of each message. Bus mastership is determined by communication of the previous transmitter and by calculations performed by the microcomputer itself.

Abstract: To permit address-free fault location on digital communication paths with several intermediate repeaters, one or more identification signals must be recognized in the intermediate repeaters with sufficient certainty. The identification signals are digital signals with periodically recurring sections which are marked with a string of successive like bits (e.g., 0 bits) and have different durations for a first identification signal and a second identification signal.The circuit contains a time discriminator (1) which responds when a string of successively received like bits is characteristic of a section of an identification signal. It then provides a pulse equal in length to this section to a frequency discriminator (2) which responds when such pulses recur at a frequency characteristic of an identification signal. The frequency discriminator thus delivers an output voltage whose amplitude is typical of one identification signal or the other because of the different pulse durations.

Abstract: A ring generator capable of supplying a plurality of predeterminedly selected distinct voltages each having a predetermined high amplitude and a predetermined frequency to a telephone line comprises a programmable computer having a low amplitude version of the plurality of voltages stored therein in digital form, the computer being responsive to predetermined control signals to select a desired one of the low amplitude version of the plurality of voltages stored therein, a first circuit arrangement coupled to the computer to convert the select one of the low amplitude version of the plurality of voltages to an analog version thereof and to increase the analog version to the predetermined high amplitude prior to coupling to the telephone line and a second circuit arrangement coupled to the first circuit arrangement, the telephone line and the computer to monitor the selected one of the plurality of voltage coupled from the first circuit to the telephone line to detect the operating condition of the ring genera

Abstract: Connection to a tantalum capacitor electrode (17) is effected using a conductive paint layer (15), incorporating pure silver and pure copper particles, which minimizes silver leeching by a tin-containing solder alloy (18) by which the lead wire (17) is connected to the conductive paint layer (15), and thus minimizes power factor degradation.

Abstract: The object of the present invention is to provide an improved convolution processor that requires no multiplication operations and can easily be implemented digitally.

Abstract: The present invention relates to a telecommunication line circuit including at least one line amplifier whose output is coupled to a telecommunication line conductor, and DC biasing means associated with said amplifier to apply thereto a DC bias signal of such a value that said amplifier cannot saturate when an AC metering signal is applied to it.

Abstract: The field component diversity antenna and receiver arrangement comprises at least a first pair of parallel spaced, straight, vertical elemental antenna elements disposed substantially parallel to the electric field component of a transmitted signal to receive the transmitted signal in a multipath fading environment where the electric field and magnetic field components are uncorrelated and a 180.degree. hybrid circuit coupled to the first pair of spaced antenna elements to provide a first output signal proportional to the electric field components and a second output signal proportional to the magnetic field component. The spaced elemental antenna elements may be monopole elements or dipole elements. The pair of antenna element may be connected together by a straight conductor to enhance the magnetic field component. The first and second output signals may be combined by known diversity combining arrangement to achieve a diversity advantage.

Abstract: An electro-acoustic transducer of the moving coil type, which includes a driven unit including a drive coil, and a magnet unit including a magnet and two pole-piece so located as to define an annular air gap in which the coil is located. The driven unit further includes a substantially circular central portion whose outer periphery is secured to the coil, and an outer portion whose inner periphery is secured to the coil and whose outer periphery is secured to a member of said transducer, which contains said magnet unit at a flat face of the member. The transducer member is substantially cylindrical. A flat cup-like member of larger diameter than the member is secured to the flat face. The driven unit also includes a cone whose inner periphery is secured to the coil and whose outer periphery is secured to the outer rim of the cup-like member.

Abstract: This invention relates to a page printer having an electro-thermal dot-matrix printing mechanism. The latter comprises at least one print plate which is disposed parallel in relation to the print line and radially in relation to the platen, which is hooked at both ends into a tensioning device. The print plate consists of a carrier plate made of material having relatively good electrical and heat-conducting properties. It is applied with its front surface to the thermo-sensitive recording medium on which recordings are made via a plurality of closely adjacent heating elements. These heating elements are deposited onto at least one of the lateral faces of the carrier plate, made flush with the front surface, and are conductively connected to the carrier plate. The remaining part of each of the lateral faces is covered, throughout the widths of the heating elements, with a layer of insulating material on which the conducting paths extending to the heating elements are disposed.

Abstract: A complex capacitive impedance (Z) whose capacitance value is considerably larger than the total capacitance of the components used in it is implemented by connecting a capacitive impedance (Z3) in series with a first resistor (R1) to form a voltage divider, and bypassing the first resistor (R1) with a voltage follower circuit (SFS).

Abstract: The covert communication system comprises a first arrangement to translate binary "1" bits into different portions of a predetermined PN (pseudonoise) code sequence and primary "0" bits into a complement of the different portion of the PN sequences, the PN sequence being selected to spread the binary signal over as large a bandwidth as possible. A second arrangement is coupled to the first arrangement to transmit the portions of the PN sequence and the complements of the portions of the PN sequence at a variable transmission rate and at a power level below environmental noise of propagation medium. A third arrangement is coupled to the second arrangement through the propagation medium to receive the portions of the PN sequence and the complements of the portions of the PN sequence imbedded the environmental noise with a fourth arrangement coupled to the third arrangement to recover the binary signal from the received portions of the PN sequence and the received complements of the portions of the PN sequence.

Abstract: The disclosed digital conference circuit additively combines conference signals with a single adder, a partial sum accumulator RAM, and conversion ROMs. Internal conferencing time slots are dynamically assignable via a microprocessor controlled channel indexing memory. The signal level on lines can be selectively adjusted to compensate for loop attenuation on a per-line basis. The circuit can operate with a number of voice coding law PCM signals from CODECs by the use of conversion ROMs containing conversion tables for the selected voice coding law. Additive background noise levels may be reduced by the dynamic selection of modified sections of the conversion tables. The number of conferences available and the number of lines per conference is limited only by the number N of internal conferencing PCM time slots. The number of internal conferencing time slots used per conference equals the square of the number of lines in the conference.

Abstract: A facility is provided for recovering the clock and data from a data stream transmitted in the bi-phase code even if the data stream contains no sync bits and if the transmission speed varies.For clock recovery, a nonretriggerable monostable multivibrator is triggered at each phase change, so that the inserted phase changes are rendered ineffective. The clock is used to control a memory which receives the valid data of the transmitted data stream at the correct instant and keeps this data constant during one clock period.

Abstract: An intruder detector system employing Doppler radar consists of an encoder for modulating RF pulses with a cyclic pulse code, the code being cycled at a frequency equal to the RF pulse frequency and the pulses being modulated on a VHF carrier for transmission along one of a pair of parallel radiating cables. The signal received from the other cable is demodulated and digitized by a zero crossing detector functioning as a 1-bit analog-to-digital converter. A bank of exclusive-OR gates functioning as 1-bit correlators then simultaneously correlates each successive bit of the digitized signal with the values of the respective bits in each fixed position of the transmitted code sequence.

Abstract: A grooming table, via one or more suction or vacuum orifices located upon or aside the grooming table work surface, is self-cleaning. Shorn animal fur or hair, resulting from the grooming operation, is drawn from the work surface into a refuse container. A vacuum or suction source is provided to the orifice or orifices via one or more vacuum containing and directing structures, all of which may be located beneath the grooming table work surface.

Abstract: A grounded tip detector for use in a subscriber line circuit detects and indicates a tip-to-ground condition in the SLIC. Hysteresis and RC filtering are provided to assure a sharp switch-over of the tip-to-ground detection output and a reduction in the effect of ripple signals due to longitudinal currents.

Abstract: A repeater for PCM or digital transmission systems includes, in addition to the usual primary feedback control loop, a secondary feedback control loop having a low-pass filter and a peak detector to derive a control signal for a controllable impedance in the equalizer circuit. This control loop optimizes the repeater performance for different cable types and characteristics with regard to the low frequency energy content of the eye diagram.