Abstract: An apparatus and method for recognition of sentences comprised of utterances separated by short pauses, the utterances representative of both isolated words and connected words. Speech to be recognized is converted into frames of digital signals. Selected ones of the frames of digital signals are compared with isolated word and connected word templates stored in a template memory. Recognition of isolated words is done by comparing the selected frames of digital signals with the isolated word templates in accordance with a windowed dynamic programming algorithm having path boundary control, while connected word recognition is accomplished by comparing selected frames of digital signals with the connected word templates in accordance with a full DPA having path score normalization and utterance frame penalty calculation capability. Variable frame rate encoding is used to identify the selected frames of digital signals.

Abstract: An electronic hybrid circuit for coupling a two-wire communication path to a four-wire communication path includes amplifier circuits having a reactive feedback path such that the output impedance of each amplifier is approximately zero ohms at DC and is a predetermined value at audio frequencies. The amplifiers are arranged to provide battery and voice signal injection on the two-wire path. Serially connected diodes provide protection from lightning.

Abstract: A subscriber line interface circuit is provided for a telephone system for interconnecting a two-wire telephone channel with a four-wire telephone channel. The circuit includes a pair of power amplifiers employing complementary circuitry and being coupled in complementary fashion to the two-wire channel so as to provide for both DC electrical excitation to the two-wire channel, as well as providing for an impedance match over the voice frequency spectrum, thereby reducing power dissipation while improving the coupling of voice and/or data signals. The presence of any noise on power line is rejected by use of transistor biasing circuits and by use of feedback circuitry. Both resistive and capacitive feedback branches are provided for the impedance matching.

Abstract: The method and apparatus to determine if a telephone subscriber line is loaded or non-loaded including circuitry to provide a signal having at least one given frequency which is coupled to a telephone subscriber line under test having a subscriber subset on-hook either directly or through the switching system such that this signal can be received from the subscriber line under test and analyzed to determine the value of at least one parameter of the subscriber line under test to determine whether the subscriber line under test is loaded or non-loaded. When the signal applied to the line has one frequency, the parameter involved is the real part of the on-hook impedance of the subscriber line under test and where a plurality of frequencies are employed, the parameter involved is either the change in the real part of the on-hook impedance of the subscriber line or a change in the phase angle of the on hook impedance of the subscriber line.

Abstract: A connecting element for chip carriers comprises a unitary pin frame of insulating material and a set of contact elements which are secured within the frame by injection molding. Each contact element comprises a wire segment having a terminal end projecting from the bottom of the frame to connect with a printed circuit board, the wire segment including a portion extending upward from the frame to serve as a spring leg for connection with a contact surface of a chip carrier. Connection may be made by soldering. The chip may be supported either on top of or hanging below the carrier. The spring legs press laterally into semicircular cutouts on the sides of the frame. Posts are provided on the frame for restricting the insertion depth of the contact elements. The posts may be formed by injection molding and may be located at miter-joint areas of pieces of the pin frame.

Abstract: An improved frequency hopped data communication system with a random transmission of mark and space frequency over the transmission bandwidth to provide independent frequency hopping of the mark and space frequency is provided in the system which is particularly immune to repeater jamming. Only one frequency is transmitted at a time upon selection on a bit instant by a pseudo-noise code generator. The location of the mark and space frequency is randomly chosen, however, the location is known at the transmitter and the repeater by appropriate synchronization equipment.

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: 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: 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: 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: 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: 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: A device is described which utilizes an addressing circuit to output, from a memory device, stored digital samples of an analog sinusoid, in logarithmic form, to a level control circuit, which modifies the digital level by means of adding a logarithmic scaler, and subsequently is encoded into a standard format, either linear, North American u-255 Law, or CCITT A-Law, and, after multiplexing with the respective bit rate. The addressing circuit has the capability to give an output with apparent frequencies in integer multiples of 8000/3989 Hz. Unused channels may be filled by a variety of digital signals, through use of a programmable memory device. Signalling control for the channels under interest is separate from the unused channels to aid in impulse noise testing. The signalling option can also be disabled.

Abstract: The frequency hopping data communications system comprises a first circuit arrangement to produce identical first and second pseudo-noise code streams time displaced with respect to each other, each of the first and second code streams producing a frequency hopping rate equal to n times the rate of binary data being transmitted, where n is an integer; a second circuit arrangement coupled to the first circuit arrangement, the second circuit arrangement being responsive to the data and the first and second code streams to provide a modulated signal for conveying the data, the modulated signal having different randomly occurring frequencies representing both binary conditions of the data and random spacing between the randomly occurring frequencies representing each of the binary conditions of the data, each bit of the data being represented by n of the randomly occurring frequencies; a third circuit arrangement coupled to the second circuit arrangement to receive the modulated signal and to separate the randoml

Abstract: A data transmission system, for interconnecting a number of relatively closely-spaced user nodes, e.g. data terminals in a computer system, uses a passive bus terminated at each end by resistive terminations (T), which bus interconnects a number of system nodes (N). The nodes are identical and there is no central control to the system. To maintain synchronism between the nodes, there is a clock/sync. pulse circuit (CSS) connected to the mid-point of the bus. This enables the use of a bit rate of twice what would be possible if the source were connected to one end of the bus due to the reduced clock pulse skew effect.

Abstract: In a telephone system, particularly a mobile radio-telephone system, incorporating statistical multiplexers and control concentrators for the arranging and formatting of digitized data, the data is formatted with operational codes designating specific meaning and any one of a plurality of levels of protection to be offered data transmitted via the telephone system. A back-up memory is connected to the statistical multiplexer to enable a retransmission of a batch of data in the event that the batch had been received with error. Full duplex communication is provided. A circular sequence number interleaved among batches of the data is utilized by an error detector at a receiving site to determine the presence of all portions of a batch of data. Transmission of specified operational codes and additional data as required in the reverse direction commands a retransmission and also provides for acknowledgement of receipt of a data batch with and without error.

Abstract: A generalized data interface for transmission of asynchronous data from a transmitting terminal to a receiving terminal at a different transmission rate is described. In accordance with the present invention, the high data transmission rates normally associated with synchronous transmission are achievable between asynchronous data terminals using novel asynchronous to synchronous and synchronous to asynchronous converters.

Abstract: The miniaturized mobile radio receiver has a straight dipole antenna whose wires run along the edge of the printed-circuit board(s) of the radio receiver and are connected at their outer ends to conductive areas. The conductive strips on the circuit board(s) which run parallel to the antenna constitute a resistive-capacitive shunt and are, therefore, open in the vicinity of the antenna base to block the flow of RF signals.