Switching network having improved turn-on capability

Claim 1

A switching system comprising a number of stages of crosspoint switching matrices arranged in order, each stage including a plurality of crosspoint switching circuits, a first set of signal transmission line groups, each group having at least one signal line and a control line, and a second set of signal transmission line groups, each group having at least one signal line and a control line; each signal transmission line group of the first set of each stage being associated with each signal transmission line group of the second set of the same stage at different ones of the crosspoint switching circuits of the same stage; each signal transmission line group of the second set of each stage except the last in order being coupled to a different one of the signal transmission line groups of the first set of the next stage in order; whereby the switching system provides a multiplicity of possible signal transmission paths between signal transmission line groups of the first set of the first stage and signal transmission line groups of the second set of the last stage; each crosspoint switching circuit including a controlled latching semiconductor device connected between each signal transmission line of the signal transmission line group of the first set and a signal transmission line of the signal transmission line group of the second set associated with the crosspoint switching circuit, and triggering means connected to the controlled latching semiconductor devices of the crosspoint switching circuit and to the control lines of the signal transmission line groups of the first and second sets associated with the crosspoint switching circuit, the application of coincident pulses to the control lines of the signal transmission line groups of the first and second sets associated with the crosspoint switching circuit causing current flow from the triggering means to the controlled latching semiconductor devices thereby switching the controlled latching semiconductor devices, when biased for conduction, to conduction and establishing signal transmission paths between the first and second sets of signal transmission line groups associated with the crosspoint switching circuit; energizing potential means connected to the signal lines of the first set of signal transmission line groups of the first stage; a plurality of biasing current control means, each connected to the signal lines of a signal transmission line group of the second set of the last stage; each biasing current control means including a source of reference potential, first switching means coupled between the signal lines of the signal transmission line group of the second set and the source of reference potential for providing a first current path between each signal line and the source of reference potential when in a closed condition, second switching means coupled between the signal lines of the signal transmission line group of the second set and the source of reference potential for providing a second path between each signal line and the source of reference potential of less impedance than the first path when in a closed condition, bistable means having a first and a second input connection and being coupled to said first switching means, said bistable means being operable when in a first condition to cause said first switching means to be in the closed condition and being operable when in a second condition to cause said first switching means to be in the open condition, said bistable means being operable to be triggered from the second condition to the first condition in response to an input signal at the first input connection and to be triggered from the first condition to the second condition in response to an input signal at the second input connection, said second switching means being coupled to the first input connection of the bistable means and being biased to the closed condition during the presence of an input signal at the first input connection; whereby the presence of an input signal at the first input connection of said bistable means during coincident pulses to control lines of selected crosspoint switching circuits switches the bistable means to the first condition causing the associated first switching means to be closed and also closing the second switching means during the input signal thereby permitting sufficient current to flow through the controlled latching semiconductor devices of the selected crosspoint switching circuits to cause the controlled latching semiconductor devices to become conductive and establish a signal transmission path through the system, termination of the input signal to the first input connection of the bistable means opening the second switching means while the first switching means remains in the closed condition permitting sufficient holding current to flow through the controlled latching semiconductor devices of the selected crosspoint switching circuits, and subsequent input signal at the second input connection of the bistable means switching the bistable means to the second condition causing the first switching means to be opened thereby interrupting current flow through the controlled latching semiconductor devices of the selected crosspoint switching circuits causing them to become nonconductive and terminating the established signal transmission path through the system.