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.