Abstract: A signal system for use in a communication system for reducing intersymbol interference to increase the data rate per cycle of bandwidth, comprising a plurality of digital channel signal states each representing a channel symbol having a plurality of bits, the channel signal states being related in accordance with the simultaneous solution of a number of equations which are the first derivatives of mean squared channel error with respect to each signal state, each equation being set equal to zero and the equations being solved simultaneously to provide the related signal states.

Abstract: An auxiliary channel, for example, an engineering orderwire, is derived on n existing time-division multiplex carrier system by modulating the pulse repetition rate of the digital bitstream. The modulating signal itself may be an analog or a digital signal. The modulator and demodulator both include a first-in, first-out shift register acting as a buffer, and the desired modulation is effected by varying the rate at which the digital information is fed out of the FIFO buffer at the transmitting end of the carrier system.

Abstract: Herein described is a drift cancellation circuit for signal amplifiers used in multiplexed data monitoring systems. The effect of analog drift is essentially cancelled and the need for an initial or periodic zero adjustment is eliminated. The elimination of the need for drift adjustment is accomplished at the analog to digital A/D converter of the mutiplexer. The A/D converter is encircuited to measure the difference between the measured input channel and a referenced voltage obtained from a sample-hold circuit. Input to the sample-hold circuit is taken from the output to the signal amplifier chain used in processing incoming channel data.

Abstract: A system for phase division multiplex duplex communication over a two-wire circuit has a master terminal and a slave terminal. The master terminal comprises a modulator and a demodulator jointly connected to a first end of the two-wire circuit and arranged to transmit an outgoing AM-signal with an essentially non-suppressed carrier component constituting a pilot signal and to receive an incoming AM-signal with a considerably suppressed carrier component having a frequency identical to the frequency of the pilot signal. An oscillator circuit is arranged to supply the modulator and the demodulator with a first and secnd, respectively, oscillator signal having a respective frequency identical to the frequency of the pilot signal and having such a relative phasing that at the demodulator the phase of the second oscillator signal is phase displaced 90.degree. relative to the phase of the pilot signal.

Abstract: In a time-division digital transmission system comprising transmitting and receiving stations interconnected by transmission lines, a number of component digital channels having a low flow rate are multiplexed into a single resultant channel having a high flow rate. The code used in the stations is a binary code and the code used in the lines is a multi-level code such that a number N of bits in the binary code corresponds to a smaller number N' of digits of the multi-level code. Consequently, a predetermined flow rate in the stations corresponds to a smaller flow rate in the lines, equal to N'/N times the flow rate in the stations.

Abstract: A balanced bridge chopper circuit including four metal oxide semiconductor field effect transistors (MOSFETs) is driven by a remote oscillator connected through an isolator to modulate low-voltage low-frequency input signals at their remote source into a square wave A.C. output signal that can be conducted to a common point where it is amplified and demodulated for better linear measurement of said low-voltage signals. The oscillator is connected through the isolator to the bridge circuit in such a manner that opposing pairs of the bridge transistors are simultaneously conducting. The isolator may comprise a novel photovoltaic isolation device or it may consist of an isolation transformer or of other types of electrical isolation devices.

Abstract: A pulse stuffing demand generating device of the kind comprising means for comparing the phases of the write clock signals HDI and the read clock signals HDL of a buffer store in which are written and read multiplexed digital information, the said store having a capacity of n binary digits, wherein the said means comprise first means for comparing the phases of the rising edges of signals HDL and HDI, the said first means supplying a pulse stuffing demand signal when the rising edge of signal HDL is located in the "one" portion of the HDI signal, and second means for supplying a signal authorizing the operation of the said first means, the said signal being supplied when one among n rising edges of the HDI signal is located in the "zero" portion of a signal resulting from the division by n of the HDL signal and the duration of which is equal to one binary digit time slot.

Abstract: A time slot interchanger for connecting data samples between locations in a telephone system, including first and second data memories for storing and transmitting data samples, a number of cross point switches, a first data bus for connecting data between the first memory and a first one of the cross point switches, a second data bus for connecting data samples between the second memory and a second one of the cross point switches, and a number of third buses connected between one of the cross point switches and a different one of the locations. The interchanger also includes a channel or control memory for storing instruction addresses for addressing the data memories and the cross point switches. The interchanger also includes a cross point control for controlling the connections of the first and second buses to the cross point switches and a time slot counter for addressing the channel or control memory, and the data memories.

Abstract: Service generator checking apparatus and a method in a telephone system operating in time frames each consisting of time slots. The apparatus sends a tone sample signal in one frame through a system interface having an input portion and an output portion, and compares the sent tone sample signal with a stored sample in a subsequent frame, thereby verifying that the interface is operational.

Abstract: A data communications or distribution loop has a plurality of computer stations each of which introduces a delay while it examines the header of each circulating packet or block of data. An elastic synchronizing buffer, including a random-access memory, is included in the loop to introduce a delay which, when added to the delays introduced by the stations, equals the period of a packet. The delay introduced by the buffer is automatically adjusted as stations are added to, or removed from, the loop.

Abstract: This invention relates to a multi-point information distribution system useful for telephone service, data connecting systems and other applications which permits a central station to service a plurality of outlying stations, through transmission media such as radio waves or wire cables, in privacy and using only one transmitting medium such as a first transmitting carrier frequency and one separate receiving medium such as a different receiving carrier frequency. The transmission media couples selected input connection points to selected terminating circuit devices one at a time. In accordance with the invention, the content on input connecting ports from a community dial office or other central system is time sampled at the central station which then transmits a sequentially ordered sample stream. Each terminating circuit or device is adapted to receive the content of only one time slot, and to transmit only during a coordinated and synchronized time slot.

Abstract: The invention relates to time-division exchanges in which the connection between the subscribers is established successively in time at the same rate as a sampling of telephone signals. It consists in offering to each subscriber circuit two incoming channels and two outgoing channels, the choice between which is made by a memory comprising an additional bit reserved for this choice.

Abstract: A TDM PCM communication system includes a plurality of user terminals, a switching network and a CPU for controlling the establishment of transmission paths between the user terminals and the switching network for the transfer of information between predetermined ones of the user terminals. An incoming path carries information bits from the user terminals to the switching network and an outgoing path carries information bits from the switching network to the user terminals. The switching network includes means for transferring single information bits each residing in a time slot period from the incoming path to the outgoing path. The transferring means includes an exchange means for effecting a bilateral exchange of information bits in fixed pairs of time slot periods, whereby paths for information bit transmission are periodically provided between ones of the user terminals, as determined by the CPU.

Abstract: A method of and an apparatus is disclosed for economically addressing memory positions in a switch memory of a transit exchange for the transfer of synchronous data signals between incoming and outgoing TDM links comprising data channels of several data rates, each constituting a multiple of a basic rate derived from the number of time slots in a TDM frame. The data signals are stored in a switch memory having a memory position for each of the data channels in the incoming links and are then transferred to a buffer memory having a memory position for each time slot of the data channels in the outgoing links before they are sent out on these links. The memory writing as well as the reading occurring at a repetition rate determined by the data rate of the respective data channel.

Abstract: Bit rate compression in a digital communications system is provided by transmitting voice information from n telephone circuits over the capacity conventionally allocated for transmission of voice information from n/2 circuits without appreciable degradation in quality. Alternatively, a doubling of the number of voice circuits may be provided with transmission at the same bit rate required for conventional transmission of voice information. Each frame period, at the transmitter, all n circuits are serviced and, utilizing an adaptive predictive encoding scheme, a maximum of only 3/8 n unpredictable samples in the given frame are transmitted over the available channel capacity.A sample assignment word (SAW), which identifies the circuits corresponding to the unpredictable samples, is transmitted therewith.

Abstract: For multiplexing 6 binary channels for example, two transcoders are respectively fed by the groups of input channels A, B, C and D, E, F in each of which is inserted a locking and identification word. Two three-channel frames in intermediate ternary form are thus obtained. Conversion into definitive ternary code (moment +, O, -) takes place at the same time as the interlacing, moment by moment, of the two three-channel frames. The demultiplexer groups the moments pertaining to one and the same three-channel frame for transcoding. The system allows high speed multiplexing.

Abstract: The disclosure herein describes a method and a system for speech detection on PCM multiplexed voice channels; for each channel, a decision is reached every M samples regarding the channel activity; in addition, the nature of speech is detected as: voiced (compact or non-compact) or unvoiced (fricative or non-fricative) when the channel is active; pure silence, white noise or echo when the channel is inactive. The decision is based on the joint value of the amplitude, zero crossing of the signal and zero crossing of the signal derivative.

Abstract: A method and apparatus are described for transmitting, over switching apparatus, digital information signals, together with a preceding address signal, wherein the address signal indicates a signal receiver capable of receiving the information signals in any time sequence. The information signals emanating from a given signal transmitter, prior to being transmitted to the switching apparatus, are individually stored, and only after a predetermined number of information signals are present are the information signals and related address signals transmitted. In the switching apparatus the address signal is used to establish a connection between the switching apparatus input and the switching apparatus output connected to the addressed signal receiver only for the period during which the information signals are transmitted.

Abstract: A method for rapidly and accurately measuring the acoustical attenuation effectiveness of various personal hearing protection devices as worn, particularly in-the-ear type protectors under conditions of normal fit in a working environment having significant ambient noise. The method comprises presenting an audio signal to an ear both with and without the hearing protector in place and noting the difference in intensity of the applied signal, measured in decibels, required to obtain the same perceived amplitude level in each case. The perceived amplitude level may be either the threshold of the subject's hearing perception or a supra-threshold reference point determined by a comparison of the test ear signal with a reference signal in the contralateral ear to allow for testing in ambient noise levels of high or fluctuating intensity. The test signal is preferably a multi-frequency complex signal having a preweighted power spectrum which emphasizes those frequencies which are particularly hazardous.

Abstract: In a digital channel bank, the binary signaling states (on-hook, off-hook) are updated periodically for each channel. Some number (n .gtoreq. 2) of the most recent of these samples are stored at the receive end of the digital system for each message channel. Under normal working conditions the output (to the switching machine) is directly influenced by the incoming real-time samples. However, when a carrier disturbance (i.e., out-of-frame condition) is detected, the updating process is stopped and the output is controlled by the older stored bits. That is, instead of sending the real-time signaling information of each channel to the switch, the signaling bits that were received and stored during a previous frame (e.g., 12 or more frames earlier) are now coupled to the switch. This assures a high probability that the proper signaling state is presented to the switch during short carrier disturbances.