Abstract: The invention relates to a wide area network implemented on a circuit-switched public data network. Terminals have access to a plurality of data channels and a control channel into the network using a balanced protocol. The invention provides a method for reducing connect time between the terminals over the data channels. To do this a conversation is established between a transaction program on the local terminal and a transaction program on the remote terminal. Responsive to generation of a frame for transmission by the transaction program on the local terminal to the transaction program on the remote terminal, a channel connection between the local terminal and a remote terminal including a data channel connecting each terminal into the wide area network is established if no channel connection already exists.

Abstract: In an ISDN communications system, a remote station power detector circuit comprises a capacitor connected between center taps of transformers on the receive and transmit pairs of conductors. The capacitor stores energy delivered from a central DC power source. Two serially-connected opto-couplers form a discharge path for the capacitor. The first opto-coupler is periodically driven on to partially complete the discharge path. If the capacitor charge exceeds a predetermined minimum, the second opto-coupler will then be driven on, providing a logic level output usable by the remote station. Power consumption is minimized by the use of large resistors in series with the capacitor while reliable power detection is achieved by detecting accumulated charge on the capacitor. Dielectric isolation is provided through the use of opto-coupler circuits.

Abstract: A data-processing subsystem diagnoses problems in one of its own subsystems, by sensing the configuration of the subsystem, displaying both text and graphic information concerning control settings and indicators on components of the subsystem, displaying information directing an operator to perform certain actions, receiving his inputs, then selecting and performing tests upon the subsystem components based upon the configuration, previous test results, and operator inputs.