Abstract: The invention relates to an interface module for the bidirectional transmission of data streams in a data network with separate power supplies for the individual bus stations. According to the invention, means are provided for bridging the bus station, preferably via normally closed contacts of a relay connected to the supply voltage and for simulating the ready condition if the power supply in the interface module fails. The latter consists of an OR circuit which is supplied on the one hand, via an operational amplifier and an RC section, with a constant delay and, on the other hand, via an optical coupler taking off the input signal, and a Schmitt trigger connected thereto.

Abstract: Method and apparatus is disclosed for identifying faults in a subscriber carrier telephone system utilizing out-of-band pilot signals and comprising pluralities of cables and repeaters that are alternately connected in series between carrier equipment at a central office location and a subscriber station. Equipment at the office location transmits selected numbers of test pulses, having a test frequency that is between the transmitted and received channel and pilot frequencies, to the first cable. The pulses are detected at the first repeater and counted. A microprocessor is responsive to the test pulse count in the repeater for initiating associated tests on the cable and/or repeater, or for retransmitting test pulses onto the next cable to the next repeater for causing it to perform designated tests. The results of the tests are sent to the office equipment in the form of reply pulses having a frequency that is below the lowest channel frequency.

Abstract: The present system employs a high speed digital signal processor which is programmed to generate pairs of digitized waveforms, each pair representing a pair of different frequencies in response to coded input signals. Each pair of different digitized waveforms, when converted and combined into an analog signal, represents a "tone pair" as used in major telephone systems. The tone pairs are transmitted through an anti-aliasing filter circuit and therefrom through amplification circuitry to a tone pair decoder of the type used in major telephone systems. At the tone pair decoder the tone pair signals are reconverted into binary signals. The binary signals from the tone pair decoder are transmitted to a data processor in the system under test, whereat they may or may not be further decoded. Ultimately the binary signals are compared with the coded input signals originally sent.

Abstract: In an electrical power transmission system, transmitter-receiver pairs at stations which communicate with similar pairs at other stations to block tripping of circuit breakers or for other control functions are periodically tested. An electrical circuit periodically activates a transmitter to send a test signal from a first station over a power line to a receiver at another station in the system. The receiver at the other station activates the associated transmitter in response to receipt of the incoming signal to send a signal back to the receiver of the first station. If this cycle is not completed in a specified time, indicating loss of communication between the two transmitter-receiver pairs, an alarm is activated.

Abstract: The system comprises at least one teleprinter station (1) connected to an exchange (3) by means of a transmission-reception line (2) and comprising a polarity detector (31) for the line circulating current, and a device (30) for reversing the connection of the line wires. If the wires erroneously become reversely connected following maintenance work on a line of single current type, then false call and conversation signals are generated which automatically trigger a checking operation in which the polarity detector is suitably examined under control of a ROM routine E controlling a CPU 84. If the current is found to be the reverse of the correct current, the reversing device is operated in order to reverse the polarity of the connection. In contrast, in the case of a double current line, the reversing device is operated when current is absent in the reception line, thus indicating an erroneous line connection. If the line current interruption is prolonged, a warning device (28) is activated.

Abstract: At a transmitter of a digital transmission system which uses a redundant transmission code to transmit data, at least one predetermined code combination which occurs randomly in the encoded data is selectively modified, to form a predetermined code violation, in dependence upon an additional signal which is to be transmitted. At a receiver, the predetermined code violation is detected and corrected to reproduce the additional signal and the data. By selection of appropriate code combinations and violations more than one additional signal can be transmitted. The arrangement is particularly suitable for transmission of additional signals, which may comprise protection switching signals or a digital voice channel signal, via fiber optic transmission links using 2AMI encoding.

Abstract: A method and apparatus for monitoring remotely-fed intermediate regenerative repeaters, in which each intermediate regenerative repeater contains a digital signal regenerative repeater for the digital data signal transmitted and a telemetry signal regenerative repeater for the generation and transmission of a telemetry signal, and in which the telemetry and digital data signals are transmitted over the same transmission line in different frequency bands, provides that the telemetry signal comprises various data blocks. Start and end are characterized by at least one start block and by two end blocks. The result of monitoring is transmitted in an error block. Moreover, a self-check during the transmission of the error block is conducted. The result of the self-check is subsequently transmitted in a test block.

Abstract: By coincidentally injecting a predetermined level of direct current with the transmission of data on a transmission line, multiple signal transmissions on the line can be detected by the presence of a DC level greater than a predetermined level on the line. Once detected, tactics for avoiding multiple signal collision problems can be implemented.

Abstract: A remote control system for a telecommunications link between two stations, one being a monitoring station and the other a monitored station, interconnected by an outward channel and a return channel, said channels having a plurality of signal regenerating member pairs. The monitoring station comprises means for transmitting by a low frequency channel and in the outward direction a sequence of P pulses, a control circuit being placed in each pair of regenerating members and comprising means for detecting the pulses received, for counting the number n of said pulses, for comparing this number with two predetermined numbers n.sub.1 and n.sub.3 with n.sub.3 .noteq.0 and n.sub.3 <n.sub.1 and when n.gtoreq.n.sub.1, transmitting to a first output n-n.sub.2 the pulses received and when n.sub.3 <n<n.sub.1 transmitting to a second output the control order and transmitting no pulse to the first output, the number P of pulses transmitted by the monitoring station being selected equal to Nn.sub.2 +n.sub.

Abstract: A repeater for use in a data communications link, particularly of the type to provide the exchange of process control information with external controlled equipment, includes a detector for detecting incoming data presented on the data communications link. Through the use of a free running internal clock, the data is retimed, reconstructed through the use of a modulator and presented to a transmitter for placement back on the data link. The repeater further provides data and clock signals to the external controlled equipment and receives signals from that equipment which serve, by way of logic circuitry within the repeater, to effect the modification of the data received by the repeater to thus enable the controlled equipment to communicate with other elements connected to the link.

Abstract: A data communication system is provided comprising, at a plurality of locations, data terminal equipment. Communication equipment adapted to transmit and/or receive data from location to location is provided at each location connected to the terminal equipment and interconnected between locations through a suitable communications channel or media. An auxiliary signal processor is provided at each location interfaced with the communications equipment and deriving from the communications equipment on a noninterfering basis, information relating to the status of the channel, communications equipment, and data terminal equipment. A central controller is provided at a central location and auxiliary communication equipment is provided at each location interconnected with the central controller and with the auxiliary signal processor.

Abstract: A digital signal repeater selecting system for a digital signal transmission system equipped with a plurality of digital signal repeaters disposed on a transmission line at desired intervals, in which there are provided in each of the repeaters a delay circuit having a particular delay time corresponding to an integral multiple of the unit code length of a digital signal and assigned to the repeater and having its input terminal connected to the transmission line, and a code comparator for comparing the input signal to and the output signal from the delay circuit with each other to produce a predetermined output signal when the both signals are decided to be substantially identical with each other, and in which when a repeater selecting code train repeating in synchronism with the delay time is applied to the transmission line, the repeater to which the delay time is assigned produces the predetermined output signal from the code comparator to allow an operation of selecting the repeater.

Abstract: A system for centralized reporting of alarm conditions in a multinode data handling system includes an alarm concentration unit at each node of the system for collecting alarm conditions. Each alarm concentration unit is coupled to a signal transmission unit which generates alarm messages and transmits the messages to a centralized node. The centralized node includes means for comparing each received messages with previously received messages stored in a memory and for amending the memory when the most recent received message differs from a previously stored message.

Abstract: A mosaic printer is made secure from unauthorized interception of data by falsifying the needle drive pulse current magnitude and sequence so that electromagnetic leakage radiation cannot be used to determine the alphanumeric data being printed. This falsification is accomplished by a compensation device having compensators energized each print cycle in addition to the printer needle drives in a reciprocal or a pseudorandom manner. The compensators have current consumption characteristics nominally identical to the needle drives and produce substantially identical radiation pulses, making it impossible to correlate the radiated pulse format with the symbol being printed.

Abstract: Input channels are provided for receiving data pulses from sensors or other parts of an electronic data system. Filters, for examle r-f decoupling filters, are provided for each channel prior to passing the pulses to a utilization device, such as a counter or the like. The shunt or grounding capacitors of the filters are tied together and connected to the output of a test pulse generator which performs two functions. In normal operation, the output circuit of the test pulse generator provides an effective AC path to ground for normal operation of the filters and their shunt capacitors. In a self-test mode, the test pulse generator provides a test pulse which is coupled through the shunt capacitors, the filters and optional wave shaping amplifiers to the utilization device for verification of the operative condition of the circuits.

Abstract: 1.

Abstract: An arrangement for checking contact betweena transmitter circuit situated upstream and a receiver circuit situated downstream, the contact being made to enable electrical signals corresponding to 1 and 0 logic states produced by the transmitter circuit to be transmitted in series to an input of the receiver circuit, is characterized in that it is formed by a first circuit situated upstream of the contact at the output of the transmitter circuit and a second circuit which is situated downstream of the contact at the input to the receiver circuit, the first circuit being designed to produce, at a first output connected to the second circuit, and if the contact is satisfactory, a current in a predetermined direction or the opposite direction in the presence of a signal representing a 1 or 0 logic state emitted by the transmitter circuit, the second circuit being designed to generate, at an output connected to the input of the receiver circuit, a signal corresponding to the logic state generated by the transmitte

Abstract: In a process for signaling an interruption in the state of readiness of a data terminal device in a called station, the data being transmitted over a data selector network, and in particular for teleprinters, following the establishment of a connection, the calling station requests the called station to transmit identification by way of the data selector network. Following reception of the identification assigned to the called station, the data transmission begins and upon the occurrence of disturbances which interrupt the state of readiness for reception in the called station, a monitoring circuit responds. For the duration of the interruption of the state of readiness the monitoring circuit blocks the identification keyer in the called station from transmitting the identification assigned to the called station and the monitoring circuit automatically clears the connection.

Abstract: A multipoint junction unit at a hub office interconnects a main line and a plurality of branch lines, the main line extending to a control station and the branch lines extending to data station line loops, to downstream local offices and to a main line of a multipoint junction unit in a downstream hub office. Normally, the junction unit broadcasts downstream data to all branches and combines upstream data from the branches for propagation up the main line. When a branch line is to be tested, test equipment connected to the upstream main line sends an address sequence to select an upstream branch and, if required, a second sequence to select a downstream branch, whereupon unselected branches are blocked and the selected branches are unblocked to permit passage of upstream and downstream data. The selected branch may thereafter be removed from the network by a "blocking" sequence which blocks the selected branch and restores all unselected branches.

Abstract: A circuit for protecting a TELEX line driver from damage due to overcurrent caused by a short circuit on the communications line. Two transistors are connected to form a monostable circuit having an input coupled across a resistor in the current path of the line driver. When current in the line driver exceeds a safe threshold value, the monostable circuit is triggered into a relatively long timed state during which the output of the monostable circuit inhibits conduction in the line driver. When the monostable circuit returns to its stable state, the line driver conducts for a short time until the monostable circuit is again triggered. Conduction in the line driver has a protective low duty cycle until the short circuit is removed and normal operation is automatically resumed.

Abstract: Power saving means is shown for use with a converter circuit in a telephone switching installation. The converter circuit comprises an analog-to-digital converter and a digital-to-analog converter. The voltage supply for the converter circuit is switched on only upon the appearance of analog signals to be converted into digital signals or digital signals to be converted into analog signals.

Abstract: A testing facility for a data communications network including modulators and demodulators, or modems, at central sites, at intermediate, or hubbing, sites, and at remote sites. Hubbing site testing units connect to respective host modems at the intermediate sites. The central testing unit transmits control words containing line address, drop address, and command characters. A configuration control circuit in each hubbing site testing unit generates signals that designate the particular location of the testing unit at the hubbing site. A validation circuit in each testing unit enables the testing unit to respond to the command character if two valid control words are received in succession. Thereafter the testing unit transmits back to the central testing unit signals in response to the test defined by the command character.

Abstract: A multipoint synchronous data network is formed by junction units which provide signal paths that interconnect incoming branch lines to a common outgoing branch. The junction units arranged to combine the branches so that data words on one branch are propagated up the common branch, subject to the condition that only one branch can send to the common branch at a time. Each data word includes a designation whether the word carries message information or control information (such as an idle branch condition). Control words are blocked by the junction unit so that message words from a sending branch are not garbled by control words from idle branches.

Abstract: In a multipoint data communications system in which a central processing unit communicates with a plurality of remote terminals over a shared two-way communications facility, an automatic fault isolation circuit is provided to monitor energy levels originating at the several remote terminals. One or more energy level thresholds are incorporated into bridging locations through which incoming and outgoing address and message signals are distributed to, and collected from, remote terminals by way of the shared facility for the purposes of detecting noise buildups and isolating trouble conditions automatically without human intervention.

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: An in-band signalling system for the transmission of both data and control signals through a common communications channel is disclosed. Unique means of distinguishing data bits from control bits is employed without the use of additional bandwidth over that which would be required for the data alone.A novel method for signalling includes the steps of translating the data bits into a different code set than the original, examining it for control words and if any are present, modifying or corrupting the data and thereafter combining on a time division basis the translated and/or modified data and control words over a transmission channel. To receive, data is inversely modified and control words detected. Error detection of control words is achieved by translating control words followed by their complements.

Abstract: A substantially non-interfering, low-intensity sweeping test signal is transmitted along a network to be tested. Means are provided for receiving and tracking the test signal at the opposite end of the network. A reference signal is transmitted along with said test signal for alerting and synchronizing the operation of the tracking means. The reference signal is at a frequency outside of the range of operating or normal signals transmitted over the network. Desirably the reference signal comprises a sweeping and a fixed frequency signal. These are then used to generate the sweeping test signal. Also, the reference signal is used by the tracking means for processing the received test signal.

Abstract: A digital display system of the dynamic pulse-lighting type for electronic desk-top calculators and the like, characterized in that a blanking signal having a pulse width large enough to cover each border time between adjacent display timing signals is used to shut off the power supply to the display devices for each pulse duration to suppress any flicker of the display unit which might otherwise result from non-synchronism or overlapping of the display signals.

Abstract: A method for indicating the free-line state of a subscriber's line connected to a terminal exchange in a binary data communication system comprising generating and transmitting to the exchange a special code word or byte of a plurality of a fixed number of "0" and "1" bits, such as alternate "0" and "1" bits. This special code word is sent after the closing signal at the end of the communication or traffic, which closing signal comprises a byte of only one "1" bit and nine "0" bits, and before the start-again-of-traffic signal, which start signal comprises a byte of only one "0" bit and nine "1" bits. The special free-line state code signal or byte not only indicates the line is free but also can, by the frequency of its alternate bits, indicate to the exchange terminal its modulation rate so that the subscriber can be automatically connected for the next traffic at this rate.

Abstract: Maximizing the printing rate of an electronic printer by causing it to print data characters at a relatively constant rate despite variations in the pattern of the incoming data. The number of characters in an incoming data pattern to be printed substantially simultaneously is monitored and the printing rate controlled within certain limits to provide a maximum printing rate consistent with the power and mechanical limits of the printer design.