Abstract: An integrated circuit has a shift register, driven by a source of clock pulses, for sequentially energizing each of a set of selectively activated switches. Each of the switches connects an analog input signal to the input of an individual sample-and-hold unit, the outputs of which are available at output terminals of the circuit. The outputs of the sample-and-hold units represent the amplitude of the analog input signal, sampled at the rate of the clock pulses applied to the shift register. The analog input signals of selected outputs are modified selectively.

Abstract: A conference arrangement for use in pulse code modulated telecommunication systems including first and second control memories and a comparison logic circuit. Two words corresponding to two channels are read from information memory during each time slot and after proper comparison, the largest sample is transmitted to a third channel.

Abstract: A digital radio transmission system including a master station and a plurality of slave stations, in which the transmit and receive periods of all the slave stations are under control of the master station. The durations and instants of occurrence of time frames are determined by a frame synchronizing pattern which is periodically transmitted by the master station on all channel frequencies of the system. The master station also transmits signalling code words for each channel frequency in fixed time slots within the frame duration as determined by successive frame synchronizing patterns.

Abstract: An initial acquisition technique for a time division multiple access (TDMA) communication system, employing an access signal of a frequency varying periodically in a predetermined relation to the TDMA time frame. Means are provided for detecting when the frequency of the signal as relayed back to the accessing station is at a predetermined value or within a predetermined frequency band to obtain the desired transmission timing information without necessitating use of any automatic frequency control means despite any deviation in the central frequency of the signal occurring during its travel.

Abstract: A system for re-establishing the orthogonality of two orthogonally polarized transmitted signals which are each provided with a beacon signal of a different frequency and which are cross-coupled when received. The received signals are fed to a decoupling network, including two controllable members for adjusting the orthogonality of the received signals, which separates the two received signals.

Abstract: Selectively seizable operating units (e.g. switches, lines or coders), forming part of different groups A, B etc. of identical units, are monitored to detect any change of state in a unit of, say, group A followed within a predetermined test period by a change of state of a unit of, say, group B. From the occurrence of the second transition, and in the absence of a switchover of any other unit of either group during the test period, an operative association is recognized between the two units in which these transitions were consecutively detected. The monitoring of all the units under surveillance is carried out in time-division sequence by cyclically scanned sensors individually assigned to them.

Abstract: Apparatus establishes a connection between a certain network input or input channel and a certain network output or output channel by rearrangement of a three-stage switching network, where, in a specific network condition, each network input or input channel is assigned to a specific network output or output channel. The desired connection is derived by means of successive permutations of the connections within the switching stages until the desired connection has been attained.The apparatus includes a special switching memory wherein the actual network condition is recorded. The organization of the memory is such that the various memory cells are addressed according to the numbering of the interstage links on one side of the central switching stage and each of the cells has a record of which network input and network output is interconnected via the link in question.

Abstract: The integrity of switched, time-division multiplexed digital trunks in a telephone switching system is verified on an individual and in-service basis wherein the digital check is accomplished incident to the conventional D.C. network path continuity verification by the switching system common controller. The terminal circuits serving the channel allow a common multiplexer-demultiplexer to insert a test code during the allocated time slot of the channel being tested and detect the same test code from a similarly-functioning testing arrangement at the far end of the digital channel. Failure of a comparison between sent and received codes results in the inhibition of a positive D. C. path check indication to the common controller.

Abstract: A conference arrangement for use in a pulse code modulated system including first and second control memories and a comparison logic circuit. Two words corresponding to two channels are read from information memory during each time slot and after proper comparison, the largest sample is transmitted to a third channel. Also included is a dial tone source for supplying dial tone to all terminations in the system by writing a time slot number assigned to the dial tone source and the respective ones of the channel memory words in the control memory associated with the channels.

Abstract: Multiplexed pulse code modulation (PCM) signals are filtered by interpolation and, at the same time, converted between different pulse code modulation sampling rates.

Abstract: A band-compressor devices designed to match to one another two systems having different pass bands, comprises means for coding input signals in the form of N digital signals corresponding, at any instant, to the amplitude of the input signal with respect to N quantizing levels. N bistable trigger stages of RS or JK type, followed by as many D-type bistable stages, are provided to receive said digital signals on the one hand and pulses furnished by a clock on the other. The output signals from the bistable stages of type D are then recombined in an adder in order to furnish analog signals or in a coder for furnishing signals in binary form.

Abstract: A portable device primarily for use in determining the effectiveness of various personal hearing protectors in attenuating hazardous noise. The device comprises an electronic circuit for generating audio test signals at varying amplitude levels, and a display for providing numerical indications usable to measure accurately the difference in amplitudes between the respective audio signals. The test signal increases or decreases in loudness in response to a subject-operated hand switch which also triggers display of the appropriate numerical indication at amplitude levels determined subjectively by the individual being tested. The electronic circuit of the device preferably is capable of producing such test signals in complex, multifrequency form with preweighting of the power spectrum of the signal so as to emphasize the most potentially hazardous frequencies.

Abstract: A switching system for use in conjunction with a high rate commutator mullexer which separates the commutator switches into two groups. During alternating off periods, each group is grounded through a switch such that voltage which is built up on the inherent capacitances of the commutator switches is reduced to zero. In this manner, crosstalk is virtually eliminated between channels of the commutator.

Abstract: An addressing arrangement is disclosed for systems in which communication is required between a main device and a plurality of associate devices. In the arrangement, access messages are used corresponding to states of shift register sequences. When the main device issues an access message, each associate device transforms the received access message to another access message which is applied to a subsequent associate device. The transformation of access messages allows the associate devices to be identical to each other and respond to the same predetermined access message since each device is uniquely identified by its location in the system. Each associate device also has the capability of being accessed by a prescribed access message which is not transformed by the associate device as it propagates through the system.

Abstract: A data transmission and display system including an input data source for transmitting data over a coaxial cable to be processed for use by a remotely-located CRT video display monitor and associated input/output devices and for receiving data over the coaxial cable initiated by the input/output devices. The data transmitted to the CRT video display monitor and to the input/output devices and the data received from the input/output devices takes the form of a plurality of successive data frames each comprising a plurality of successive data intervals. In the first interval of a frame, data is transmitted by the input data source over the coaxial cable in a forward direction to be used by one or more of the input/output devices for performing certain operations specified by the data. In the second interval of the frame, data which may be initiated by one of the input/output devices is transmitted over the coaxial cable in the reverse direction to the input data source for utilization thereby.

Abstract: A plurality of communicating stations have transmitters, receivers and control means. The transmitters are tunable across a broad radio frequency spectrum and transmit an amplitude modulated selected carrier frequency. Each receiver is set to receive only one preselected amplitude modulated carrier frequency fixed and identified with each particular station. Stations may be regarded as telephones having signaling means and a chassis. The control means includes means to receive TDM control signals from and to supply TDM control signals to a remote common equipment unit. The control signals and amplitude modulated carriers are sent and received over common cabling. The common equipment unit includes processor means to process and generate control signals and means to interface with an external telephone system.

Abstract: An echo suppressor employed in systems interconnecting a two-wire circuit with a four-wire circuit for substantially eliminating "talker's echo" and for selectively attenuating the calling party's voice signal when the called party at the two-wire line begins speaking. The signal levels of signals on both paths of the four-wire circuit are measured to extract the maximum values of the signals for succeeding time intervals. The extracted value of the outgoing path signal is divided by the extracted value of the incoming path signal to generate an attenuation factor value. This value is multiplied by the value of the voice signal in the incoming path to generate an estimated leakage level signal. When this level is greater than the signal level in the output path (i.e. when there is no outgoing voice signal) the outgoing path is disconnected to prevent a talker's echo signal from being transmitted thereby.

Abstract: The recurring time slots in each line of a time division multiplex communication system are identified by a unique combination of phase relationships among a plurality of synchronization signals. Each of a plurality of terminators sends and receives samples of input and output data to and from an information path consisting of a bundle of discrete lines or buses. Any particular connection involves only on a selected line or lines and is gated to appropriate terminators only during recurring preselected time slots and only via a selected line or lines. Time slots are identified by a unique combination of phase relationships occuring in a separate synchronization path.

Abstract: Disclosed is an automatic data communication system having communicating modems equipped with automatic equalizers. The equalizers respond to a first long equalization sequence automatically transmitted from another modem. In response to that long equalization sequence, the equalizer starts from a preset non-equalized condition and assumes a fully equalized condition. That equalized modem is also capable of automatically transmitting its own long equalization sequence to the other modem. Thereafter, second short equalization sequences are employed at the receiving modems to enable a memory storage associated with the automatic equalizers. The memory stores, in response to the long equalization sequence, signals which are indicative of the fully equalized condition. Accordingly, the equalizers do not have to start from a non-equalized condition for each new data message unless a dramatic distortion occurs.

Abstract: Interchange of data between two way loops and a data trunk is provided by way of channel units, submultiplexer/demultiplexers and a common multiplexer/demultiplexer. Submultiplexers have five, 10 or 20 ports, creating time frames with corresponding numbers of time slots, all of equal duration. The channel units, which terminate 9.6, 4.8 or 2.4 Kbs data subscribers, assemble the incoming data into bytes, repeat each byte five, 10 or 20 times, respectively, and align each successive one of the repeated bytes with successive time slots. Any port of a five port submultiplexer can be connected to any 9.6, 4.8 or 2.4 channel unit. Similarly, any port of a ten port submultiplexer can be connected to any 4.8 or 2.4 channel unit and any port of a twenty port submultiplexer can be connected to any 2.4 channel unit. The outputs of all submultiplexers are interleaved by the common multiplexer and applied to the trunk.