Abstract: A device for automatically reading one or more meters at a remote location and supplying the information read over telephone lines to a central station includes a coupler effective on command from the central station to furnish power to the meter reading device from the telephone lines and to energize the device to duplicate the readings of the meter counters in sequence to respective registers, from which the readings are encoded in an encoder effective to transmit the information through the coupler and over the telephone lines to a central station by frequency-shift modulation, and to repeat the message until signalled by the central station to stop.

Abstract: In a sound reinforcement system having a plurality of input channels and input signal sources and at least one output channel, a gain control apparatus is provided for controlling the gain applied to the signals in each channel whereby the total gain of the system remains constant. Gain changes in each channel are proportional to signal ratios such that the automatic gain variations in all channels are always complementary. In a preferred embodiment, the control apparatus comprises means for providing a reference signal having a magnitude proportional to the sum of the amplitudes of the signals in the channels and a plurality of control signals each of which has a magnitude proportional to the amplitude of the signal in a respective one of said channels, and a plurality of attenuating means, each of which is responsive to the ratio of the corresponding one of said control signals to the reference signal.

Abstract: An automatic gain control circuit for limiting the acoustical power to the receiver portion of a telephone operator's headset. The circuit provides means whereby the maximum level of acoustic energy output a telephone operator is subjected to is controlled to levels well below those where damage to the ear can occur. Features of the invention include the use of diodes in the feedback path of the an amplifier whereby DC currents control the conductivity of the diodes to control the amplifier gain, and a pair of such circuits in phase opposition serve to cancel control current effects on the signal path.

Abstract: An acoustical wave filter is formed by depositing a pattern of interdigitated conductors which form a coding arrangement on a piezeoelectric crystal. Multiplex communication through the crystal is achieved by depositing input filters of differing configuration on the crystals, which separate channels by autocorrelation of a pulse code. A single output filter is provided to respond to the waves set up in the crystal by the input filters to transmit these waves to a single common conductor. Demultiplex is similarly done on a second crystal.

Abstract: A system is disclosed for safeguarding data against slip in signals occurring in interfaces between exchanges employing different exchange clock rates. Suitably connected storage arrangements cause the instants of slip compensation in both directions of transmission to coincide. In this way, omission of a signal in one direction of transmission results in a signal being inserted in the other direction and prevents the loss of data.

Abstract: A reverberation system which employs low cost, spring reverberators and obtains a frequency response to beyond 9kHz. The high frequency components of an input signal are frequency shifted, to a lower range, applied to a reverberator, and then frequency shifted to their original range. This signal is then summed with the output of a second reverberator which receives the lower frequency components of the input signal.

Abstract: A computational algorithm and an implementation thereof is described herein for determining the pitch period of voiced speech in real time. All processing is performed in the time domain employing the prediction residual or error signal of a 10th-order Itakura cascade adaptive linear predictor or filter as the input signal. The output (pitch period) of the algorithm and the implementation thereof is updated each sample period based on analysis of the present and past input samples. Pitch period is determined by locating the sharp pitch peaks in the short term power of the prediction residual. The instantaneous pitch period is the time separation of two adjacent pitch peaks. The algorithm and implementation thereof employs a time moving search window and a time varying threshold level to locate pitch peaks. Various tests and procedures are incorporated into the algorithm and the implementation thereof to handle the special cases of false and missed pitch peaks.

Abstract: A power spectrum analysis of the harmonic content of a voiced sound signal is conducted in real time by phase-lock-loop tracking of the fundamental frequency, f.sub.o, of the signal and successive harmonics h.sub.l through h.sub.n of the fundamental frequency, measuring the quadrature power and phase of each frequency tracked, differentiating the power measurements of the harmonics in adjacent pairs and analyzing successive differentials to determine peak power points in the power spectrum for display or use in analysis of voiced sound, such as for voice recognition.

Abstract: A time division switching system is disclosed having a plurality of telephone line circuits and common control circuits for switching calls over a time division communication bus. Ringing loop current detectors are shared by groups of the line circuits for detecting call answer signals during active ringing on a call and for controlling the line circuits to interrupt, or trip, the ringing upon a called party answer. Each group of the line circuits is permanently connected to a ringing current supply via an individual one of the loop current detectors. Each line circuit includes ringing control circuitry operated and released by the common control circuits for connecting ringing current to a called line during an active ringing interval and for disconnecting it during a silent interval of the ringing cycle. The circuitry is responsive to a detection of a called station answer signal by the shared loop current detector for immediately tripping ringing.

Abstract: A speech aid device has a housing with a tubular main body enclosing a battery and an electric motor. An obliquely directed side arm of the housing has a diaphragm resiliently mounted at the free end. A striker is guided for reciprocable movement along the side arm axis to beat against the other face of the diaphragm and is driven by the motor through a gear box and an eccentric drive. A tension spring is included in the drive and a compression spring opposes the striker return movement, so that the striker is floatingly mounted by the springs. A feature of the drive is a resilient link between the motor and hammer.

Abstract: Ringing loop-current detectors are shared by groups of telephone set line circuits. A time division switching system is disclosed having a plurality of telephone line circuits and common control circuits for switching calls over a time division communication bus. Ringing loop current detectors are shared by groups of the line circuits for detecting call answer signals during active ringing on a call and for controlling the line circuits to interrupt, or trip, the ringing upon a called party answer. Each group of the line circuits is permanently connected to a ringing current supply via an individual one of the loop current detectors. Each line circuit includes ringing control circuitry operated and released by the common control circuits for connecting ringing current to a called line during an active ringing interval and for disconnecting it during a silent interval of the ringing cycle.

Abstract: Characters which repeat between successive groups or lines on a page, are, except for an initial transmission, not transmitted, thereby decreasing the time for data transmission. Only the non-repeat characters between the successive groups or lines are transmitted along with a "map" (i.e. a sequence of numbers) indicative of the format of the repeat and non-repeat characters of the present group, or line, so as to enable a receiving station to reassemble the compressed data. A new map need not be sent, thereby further decreasing transmission time, if the transmission using an old map which has been previously transmitted compares favorably with the transmission using the new one.

Abstract: A complex waveform synthesizer comprises a plurality of digital oscillators producing unit waveforms at distinct frequencies and constituted by respective storage zones storing, as digital words, the momentary values of the waveforms. The required amplitudes of the waveforms are produced by a digital modulator supplied with trains of digital desired amplitude values from a digital interpolator receiving corresponding trains of desired digital values at a slower rate than those supplied by the interpolator. The modulator supplies the waveforms, with an amplitude definition greater than that of the desired values supplied to the interpolator, to a digital accumulator which combines the digital words it receives to produce a series of digital words defining a complex waveform which is the sum of the individual waveforms defined by the series of words emerging from the modulator.

Abstract: A digital speech compression system uses a predictive feedback loop. The digital speech signals are compressed within the feedback loop for reducing the transmitter bandwidth. The system comprises a first adder into which the digital signal is fed followed by a quantizer and a compression logic. The predictive loop includes a second adder coupled to the compression logic and followed by a digital predictive filter. The output of the filter is impressed in a negative sense on the first adder and in a positive sense on the second adder. Specifically, the quantizer and compression logic may consist of a two-valued limiter followed by a compressor and a converter in the feedback loop or alternatively the limiter may be followed by a converter while the compressor is disposed outside the feedback loop to provide sample by sample compression.

Abstract: A time division switching system is disclosed having a plurality of telephone line circuits and common control circuits for switching calls over a time division communication bus. Ringing loop current detectors are shared by groups of the line circuits for detecting call answer signals during active ringing on a call and for controlling the line circuits to interrupt, or trip, the ringing upon a called party answer. Each group of the line circuits is permanently connected to a ringing current supply via an individual one of the loop current detectors. Each line circuit includes ringing control circuitry operated and released by the common control circuits for connecting ringing current to a called line during an active ringing interval and for disconnecting it during a silent interval of the ringing cycle. The circuitry is responsive to a detection of a called station answer signal by the shared loop current detector for immediately tripping ringing.

Abstract: An improved loudspeaking telephone system including voice switching is disclosed. The system is bistably voice controlled by inversely regulating the impedances of variolossers in the transmit and receive channels, respectively. Hysteresis is added to the bistable control by the summation of receive and transmit signals across a plurality of unequal impedances that form part of an input control means. Circuitry forming the input control means also includes transmit noise guard circuit means useful in discriminating between ambient noise signals and syllabic speech signals. Further, a novel receive noise guard circuit means is used to discriminate between syllabic speech signals and high level noise transmissions from another station. The outputs of both the transmit and the receive noise guard circuit means are summed with the transmit and receive signals across unequal impedances to prevent seizure of the bistable control by ambient noise and to improve the receive channel sensitivity.

Abstract: A Digital/analog conference arrangement for up to M (15) digital subscribers. The digital signals are sensed, and up to N (3) are converted at the same time to analog signals which are processed in an analog bridge, then converted to digital signals which are transmitted to the appropriate subscribers. The voice signals of each subscriber are encoded by the continuously variable slope delta modulation (CVSD) technique into a serial digital bit stream, which are time-multiplexed into 15 input channels.

Abstract: A hearing threshold level measuring apparatus for automatically determining testing hearing level in each ear and processing the test scores for either manual or automatic readout. A predetermined number of tone bursts varied randomly from one to four in each test sequence and automatically decreased in level. The subject is provided with a response panel containing pushbuttons labelled one through four. The subject's bearing threshold is then determined from his pushbutton responses to his correct burst tone counts.

Abstract: A delay line which disappears under voice control is comprised of a pluray of shift registers delays the incoming voice signal to permit transmission of the voice scrambler preamble. The delay is removed over a period of time during speech transmission by removing a segment of the delay line each time a pause of a specified length is detected in the speech.

Abstract: Multiplexer for telephone transmission coupling the calling channels containing supervisory information which are not premodulated to the premodulated conversation channels which contain the voice information, modulating the coupled channels to bring the conversation signals into the multiplex group and using a single extra modulation of the whole spectrum obtained after modulation of the coupled channels to re-position correctly the calling signals in the multiplex group.