Abstract: Pulse Code Modulation (PCM) translator for translating a PCM input word into a PCM output word, one of said words being in accordance with a compressed code and the other with a linear code, characterized in that it is adapted to convert the binary bits of the input word into those of the output word in accordance with either the A-law or the mu-law. The circuit forms part of a telephone line circuit (LC) connected between a telephone line (LI) and a digital switching network (SNW) and comprising the cascade connection of a subscriber line interface (SLIC) able to perform line control and supervision, a digital signal processor (DSP) mainly adapted to execute analog-to-digital and digital-to-analog conversion operations, the above transcoder circuit and a dual processor terminal controller (DPTC) which deals with the general control of the line circuit. The DSP only processes linear PCM signals, whereas the DPTC solely operates on companded PCM signals.

Abstract: A keypad is formed of a set of transparent buttons slidably located within apertures of a grid. The grid has sidewalls for engagement with the base of a printed circuit board. Switch assemblies are provided by conductive elastomeric domes formed of a single sheet of elastomeric material disposed between the printed circuit board and the buttons. Integrally formed within a concave side of each dome is a contact region driven by a displacement of a button towards the printed cirucit board. An insulating layer above strip conductors of the circuit board is perforated at sites of the switches to allow the contact region to touch the exposed portions of the conductors to complete an electrical circuit. A dome deforms with springiness which urges the dome back to its original shape upon release of a button by a user of the keypad. Manufacture of the keypad is facilitated by construction of a set of the butons on a webbing which maintains alignment of the buttons as they are secured to the respective domes.

Abstract: In a cellular mobile radio-telephone system, a hand-off procedure is implemented by use of idle voice channel transceiver at relay stations of cells contiguous the site of a mobile station. The receiving portion of each transceiver is provided with tuning circuitry permitting a detuning from a preassigned idle channel frequency to the present broadcast frequency assignment of the mobile station. A set of measurements of broadcast signal is made at the detuned idle channels to determine the cell of best signal. The mobile station is then handed off to the cell of best signal.

Abstract: An integrated circuit for a telephone instrument provides the basic (POT) service requirement. The transmit and receive channels of the circuit may be fed via controlled attenuators incorporated in a first ancillary circuit to provide hands-free operation. The circuit also includes a current-limited power supply whereby connection to a second ancillary circuit, including an audio amplifier, may be effected to provide loudspeaker operation.

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: In a transformer-coupled interface circuit for interconnecting two-wire and four-wire telephone communication channels, there are provided a bucking winding in the transformer and a flux compensation circuit which drives the bucking winding. The flux compensation circuit includes a sensor of direct current current flowing through a primary winding of the transformer for applying power to a subscriber telephone. Also included within the compensation circuit is a current source responsive to the measured primary current for controlling the magnitude of the bucking winding current to track the primary current, thereby to reduce the flux in the transformer core and permit use of a smaller sized core. A stabilization circuit within the current source prevents oscillation resulting from feedback and reactive circuit components.

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: 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: 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 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: A frequency hopping data communication system which provides reliable communication in a fading environment and also which is jam resistant is described, in which an improved frequency hopping data communication system provides reliable communication in a fading environment such as in a mobile, satellite or scatter communication systems. Pseudo-noise code streams are time displaced with respect to each other, and provide a frequency hopping rate equal to n times the rate of repeated binary data being transmitted, and wherein the pseudo-noise codes are used to directly derive a hopped frequency from a selected code sequence.

Abstract: An instrument for measuring the distance of a body in relative motion away from a datum point measures the optical attenuation of an optical fibre that has an end secured to that datum and extends to the body where the remainder of the fibre is coiled. As the body moves away, so progressively more fibre is uncoiled, and the contribution of bending losses to the total loss is reduced and hence the resulting reduction in attenuation provides a measure of distance travelled.

Abstract: A modulator circuit produces an AM modulated output signal by modulating a low rate digital signal on a higher rate data signal. The modulator circuit operates to switch the ground return of a line driver circuit which selectively amplifies the high rate data signal and has its ground return switched in accordance with the lower rate digital signal to produce an output modulated signal of a three level modulation characteristic whereby the modulation index of the signal is selectable by varying the impedance in series with the ground return of the line driver. A demodulator for the output signal of the modulator incorporates circuitry by which the high speed data carrier signal is first retrieved and is then subtracted from the modulated signal to yield a separate high speed data signal and the low speed digital signal with an enhanced signal-to-noise ratio.

Abstract: The present invention discloses a feedback control circuit in which the input and feedback signals are processed by making use of the same capacitance so that there is no problem of capacitance matching. Another aspect of the invention is a sigma-delta modulator in which the processing means includes integration means which are able to integrate said sampled and added input and feedback signals and to provide an analog output signal, a one-bit analog-to-digital converter providing a digital output signal in response to said analog output signal, and a one-bit digital-to-analog converter providing said feedback signal in response to said output signal, said input signal being sampled and simultaneously said converters being operated by and during first of said timing signals, while by and during second of said timing signals said feedback signal is sampled and said input and feedback signals are added and integrated, said first and second timing signals being non-overlapping and defining a sampling period.

Abstract: In an optical fiber FDM system, the carriers are derived from the output of a high quality Master Oscillator, which output at frequency f.sub.0 is applied to a Raman Nath modulator (RNM1) whose other input is a frequency f.sub.0 this gives as its outputs (assuming a five channel system) f.sub.0 -2f, f.sub.0 -f, f.sub.0, f.sub.0 +f and f.sub.0 +2f. These are modulated by modulators (CM1, to CM5) with the signals to be sent, and the modulation results combined in a combiner CB for transmission to a remote station. The oscillator output is also sent to the remote stations where it is frequency-shifted by a Bragg modulator (BM) and the resultant similarly dealt with by a Raman Nath device (RNM2) to give five frequencies which are used to demodulate the channels. In an alternative the channel frequencies are switchable.

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: A multiple fiber linear array comprising a pair of spaced apart plate members separated by spacers having a diameter no greater than the diameter of the largest fiber in the array and defining a passageway in which the fibers are inserted such that the fibers terminate adjacent one end of the passageway and are parallel and contiguous throughout a substantial portion of their length in the passageway.

Abstract: To monitor the course signals radiated by the two-frequency glide-path station with respect to course line and course width, and to monitor the clearance signal, the signals radiated by the antennas (A1, A2, A3) and a signal extracted directly from the transmitter (1) are so combined (5, 6, 7) that the clearance signal (CL), the sideband signal (SBO), and the carrier and sideband signal are obtained. These signals are evaluated (8) for monitoring purposes in a manner known per se.