An automatic fault detection and modem bypass circuit for a standard land line data transmission system containing a plurality of series connected modems arranged in a conventional hub configuration is disclosed. A relay is located in a central collecting station of the hub and connected so as to open an input line to at least one of the modems and an output line from a line amplifier connected to an output line of the same one of the modems upon the occurrence of a fault in the input line to such modem. A series connected combination of an amplifier and a switching transistor is responsively connected to the output line of such modem and operatively connected to the coil of the relay to simultaneously disconnect such modem from the series connected hub group and connect an output line from a line amplifier immediately preceeding such modem in the series connected group to an input line of a modem which next succeeds such modem in the group. Means is provided for listening to the various signals on the input and output lines to and from each of the modems to enable a trained operator to locate faults in the system by sound. An additional feature includes a relay switch connected between the output terminals of a modem and its output line which is responsive to a fault on the input line to such modem so that the automatic bypass circuit can be made to remove the modem from the series connected group upon the occurrence of a fault on either an input or an output line to or from such modem. The circuit of the disclosure permits a given modem in a series connected group of modems to be removed from the group without disrupting the operation of the remaining modems in the group.
An interface apparatus for interconnecting signal lines of a computer connector and a peripheral device connector with non-matching interconnect patterns having mismatched data lines or open inputs on handshake or control lines. A pair of conductive paths extend between the connectors, with each path interconnecting one data line of the computer connector with one data line of the peripheral connector. Lights indicate mismatched interconnection of the data lines, and a switch selectively reverses the interconnection of the data lines. Additional conductive paths extend between the connectors, each path interconnecting at least one handshake or control line of each connector with at least one handshake or control line of the other connector. Two pairs of interconnecting handshake lines are each provided with a switch in gang with the data line switch for selectively reversing their electrical interconnection. Four current-regulating field-effect transistors are each connected between one of the handshake lines and a common node, and act as a conductor when an enable signal is present on its line and as a current-limiter when an open input is present on its line. Resistors are connected between the common node and each of the remaining handshake or control lines.
In a data communication system including a plurality of remote units under the control of a master controller, whereby each of the remote units operates to transmit and receive data from the master controller, an interface circuit for connecting each remote unit to the controller includes a switching transistor operable via a timing network for turning on to apply a high level signal continuously on the remote data output terminal of the associated interface circuit, for effectively isolating the malfunctioning remote transceiver, while permitting normal system operation without interference from the malfunctioning unit.
An audible test termination device for providing a characteristic signature to the telephone central office and an audible signal to the customer when a continuity test is made on a subscriber line having a pair of electrically conductive paths includes a miniature audio indicator and a minimum of associated electrical components to indicate to the central office test operator and the customer that the telephone subscriber line is in operating order. One embodiment of the instant invention may be utilized as an additional high impedance ringer for the customer. The present device may be permanently installed across the subscriber line.
A local area network is provided with increased tolerance to faults by arranging multiple hubs in nodes in the network. Internal connections in each hubs of the same node upon detection of a failure to provide an alternate path for data transmission in the network.
A modular system for controlling the routing of data through a plurality of data terminals includes a number of modules in a tree structure. Each of the modules has circuitry for receiving a data stream. Each of the modules further has a plurality of ports, each port being suitable for transmitting data to and receiving data from data devices such as data terminals and other modules. Each of the modules includes a routing array connected to the ports for serially connecting the ports for flow of the data stream through the operable data devices connected to the ports. The routing array is internally controllable to open a selected one of a plurality of data paths between the ports. At least some of the ports have driver circuits associated therewith for regenerating and converting the data stream as it passes between ports in the selected data path. Each module has an output for supplying the data stream from the module to a destination device. Detecting circuitry is included in each module for automatically detecting a fault between the input and output of that module. The detecting circuitry is responsive to the detection of such a fault to control the routing array to open a fault-free data path between the input and output of the module if any such path exists.
