Abstract: A monitoring tap for accessing signals on bus or tag coaxial cables used to convey signals between a CPU an external devices is described. A circuit board carrying termination resistors for the coaxial cables and high input isolation amplifiers is provided with an input connector that mates with the plug located in the slot that normally receives a terminator. The circuit board has an output connector coupled to the outputs of the isolation networks. A housing partially encloses the circuit board while enabling external access to the output connector. Several embodiments are described.

Abstract: A switch matrix system is described with which peripheral devices can be conveniently tested for compatibility with central processor units. A diagnostic channel is provided to which a peripheral device to be tested is connected at a crosspoint in the switch matrix system. A control provides a sequence of signals needed to establish data communication between the central processor unit and the peripheral device. Errors or failures in the sequence are detected and stored and displayed with a terminal from which the switch matrix system is operated. Additional testing is done by generating bit test patterns and comparing the returns with those sent out. A channel activity monitor is employed in the switch matrix system to enable a comparative review of activity of channels from different central processor units.