Abstract: A method and apparatus for transmission line termination is provided in which a transmission line (12 and 14) is terminated by transmission gates (20 and 22) at a transmitter (24) and a receiver (26). The resistances of the transmission gates (20 and 22) are controlled by precision resistance control circuits (30 and 31), respectively. Precision resistance control circuit (30) uses a reference resistor (32) to control the resistance of the transmission gate (20).

Abstract: A DC termination circuit is provided for keeping a sealing current on a subscriber line during normal operation in order to prevent an oxidation of contacts in said line. The termination circuit is coupled across the line in response to the normal relatively high line voltage. In order to test the line, especially for its electrostatic capacitance, the line voltage is switched off and a relatively low voltage is applied through test equipment to the line. Responsive thereto, the termination circuit is removed from the line to terminate the sealing current.

Abstract: A station diagnosis method in a communications network system including a closed ring transmission line and a plurality of data stations which can be connected to the ring transmission line by a plurality of line concentrators disposed in the ring transmission line wherein an internal ring transmission line is formed in the line concentrators so that the operation states of the line concentrators are diagnosed by transmitting diagnosis data through the internal ring transmission line.

Abstract: A circuit for restoring and converting bipolar customer data signals into a pair of binary signals at a customer data frequency equal to or less than 250 KHz includes a PCM integrated circuit repeater for restoring and converting 1.544 MHz communication signals and transmission lines. Use of the high frequency repeater is enabled by a buffer amplifier connected in series with the input of a repeater amplifier and which has an input connected to a parallel resistance and capacitance network which is connected in series with an ALBO diode of the repeater for automatically inserting loss characteristics in the input signal so that the input signal has characteristics resembling losses of a signal passing through a maximum length transmission line. Fixed equalizer and amplification circuitry restores the original pulse signal magnitude and characteristics.

Abstract: A data transmission circuit is disclosed which is arranged so that when transmitting data and control signals of a terminal equipment accommodated in a transmission line of 64 Kbps channels through use of a multi-frame arrangement, the data is assigned to a required number of bits in a predetermined number of frames in the multi-frame or adjacent ones of the predetermined number of bits and at least one synchronization flag bit and various control signals are assigned to the remaining bits but a request to send signal and the synchronization being assigned to one of the remaining bits according to the logic OR of their succeeding sampled values, whereby data of different transmission speeds can be transmitted by the same circuit.

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: A coupling discriminator for Ethernet standard local area network interface equipment monitors the electrical characteristics of an incoming differential signal pair, discriminates between a signal pair that is direct coupled and a pair that is transformer coupled, and configures the interface equipment for operation with the type of coupling detected.

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: An interface unit is disclosed which can make asynchronous data communication between a transmitter unit and a receiver unit. The interface unit includes a shift register for receiving start data designating a start of data input and input data from the transmitter unit. The start data is used as an interruption signal indicating data input to the receiver unit and is used as an inhibition signal for inhibiting clock application to the transmitter unit. The inhibition of clock application is removed by a control signal transferred from the receiver unit to the interface unit. Clock application to the transmitter unit is restarted in response to the control signal, and a next new data is transferred to the interface unit. Thus, the interface unit can easily and smoothly control asynchronous data communication between the transmitter unit and the receiver unit by means of simple circuits.

Abstract: A facsimile communication system equipped with an ARQ function for transmitting data in the form of a block between a transmitter and a receiver through a transmission route having a relatively large time delay, such as a submarine cable and communications satellite, is provided. In the system, prior to transmission of image data, a time delay in transmission of data through a selected transmission route is measured and the number of bits of data block is determined in accordance with the thus measured time delay.

Abstract: Apparatus operable without need for an external power source for conveniently interconnecting data communication equipment (DCE), such as a modem, and multiple data terminal equipments (DTE), such as terminals and/or printers, which each have an interface conforming to a serial data communications standard, for permitting access to the DCE of any of the DTEs that may be connected to the apparatus. In the preferred embodiment, intended for the interconnection of interfaces conforming to the E.I.A. RS-232-C standard, a circuit interconnecting the data leads of a multiplicity of pluggable cable connectors supported on a chassis includes a transistor connected to be powered by input data signals from the DTEs and to operate as a switch under certain signal conditions and to be effectively removed from the circuit under other signal conditions.

Abstract: The circuit (10) has a gain section which includes a first AGC circuit (12). The output of the gain section goes to a signal shaping section which includes a biquadratic filter (24), a summer (45), and a second AGC circuit (40). The two AGC circuits (12,40) are controlled by respective separate peak detectors (20, 50) and are noninteracting. For "short" cables, only the first AGC circuit (12) is active. For "long" cables, the first AGC circuit (12) is set at its gain breakpoint and the second AGC circuit (40) alone has active control. The shaping section includes a biquadratic filter (24) which is a tandem arrangement of a low-pass filter (26), an inverter (28), and an integrator (32). The low pass output (35) of the integrator (32) is connected to the noninverting (+) input of the a summing amplifier (45). The input (42) of the second AGC circuit (40) is connected to the band pass output (33) of the inverter (28), while its output (44) is connected to the inverting input (-) of the summing amplifier (45).

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: An interface for connecting data terminal equipment (DTE) to data communication equipment (DCE) is provided which requires no modification to an existing and widely accepted DCE connector and yet which permits data communication according to more recently adopted functional interface standards through the same DCE connector. Specifically, in a single 25-position interconnection configuration for DTE, an interface is provided which supports (1) the EIA Standard RS-232C interface with unbalanced generators and receivers at generally established RS-232C pin assignments at a DCE terminal junction; (2) an RS-449-type interface with balanced generators and receivers with pin assignments at locations incapable of being confused with RS-232C interface connections at a DCE terminal junction; and (3) an RS-449-like interface with balanced generators and receivers in a variety of multiple-point applications.

Abstract: An electronic d.c. telegraph transmitter comprises a transmitting keying circuit and a current regulating circuit which operates in accordance with the principle of a continuous regulator and serves to maintain the line current constant. The power loss which is converted into heat is as small as possible. Between the current regulating circuit and the telegraph battery, a switching stage connects only one tap of the telegraph battery to the input of the current regulating circuit. The voltage present at the input of the current regulating circuit is automatically increased or reduced in stepped fashion in dependence upon the transmitting voltage which occurs on the transmission line.

Abstract: Optical receiver arranged to provide a dispersion-compensated detection of digital information transferred by a light pulse train via a fibre optic conductor, includes a registering means and a timing regenerating means connected in parallel to the fibre optic conductor via an optoelectrical converter. The registering means has a sampling terminal, an activation input that is arranged for a short activation of the sampling contact and which is connected to the timing regenerating means, and an output that is arranged for reproducing the registered digital information transferred by the light pulse train. According to the invention, the optical receiver has a decision means with a decision level determining input supplied with a control voltage obtained from the output of the registering means via a digital-to-analog converting link and is interconnected between the optoelectrical converter and the sampling contact of the registering means.

Abstract: A transmission circuit including cross coupled transistors is described. The circuit is symmetrical and the base of each transistor is coupled to the collector of the other and also to a supply voltage through a voltage divider. The output is taken across the emitters of the transistors. Switching circuits which are coupled to the voltage dividers change the resistance of the circuit and effect an output signal. The symmetrical configuration of the circuit and the cross coupling make the circuit insensitive to temperature changes.

Abstract: An electronic switch arrangement reverses damping of an electronic switching element by means of a controllable negative resistance. Adjustment of the negative resistance is provided by comparing a measuring current through the arrangement to a preselected reverse current.

Abstract: A line device for transmission lines having coaxial cables for the transmission of signals, in particular digital signals or analog signals, employs an input equalizer in the form of a line section connected in parallel or in series to the transmission path, a first switch or dividing network for dividing the transmission path into a communications transmission path and a long distance current supply path, a regenerator in the communication transmission path, a series circuit connected in the long distance supply path including a first low pass filter, an element for producing a voltage drop for the current supply of the regenerator and a second low pass filter. A second switch or dividing network rejoins the communications and long distance supply paths and an output equalizer in the form of an additional line section is connected in parallel to the transmission path or in series with the transmission path.

Abstract: In a system including several devices connected by means of a common data bus the adverse effects of reflections due to two or more devices simultaneously seeking access to the bus are minimized by confining such reflections to parts of the bus remote from the devices. This is achieved by preventing the amplitude of a signal at a receiving station on the bus from exceeding a predetermined level; and integrated circuit serving as a near ideal diode clamped to a reference voltage performs this function.