Abstract: A driver is utilized at the output of a digital word generator for translating a digital word to selectable voltage levels in accordance with a particular unit connected to the output of the driver and undergoing diagnostic testing. The driver has a separate control line for switching the driver to a tri-state mode so that the input of a unit undergoing test may be switched to a high impedance input, thereby permitting tri-state diagnostic testing of a unit undergoing test.

Abstract: A programmable logic shifting interface circuit provides programmable high and low level output signals from TTL input signals. Programmable upper and lower logic levels are available at the output so that a wide variety of different digital circuits may be tested by the invention.

Abstract: A programmable multi-channel signal analyzer capable of automatically evaluating and displaying various parameters of complex analog waveforms is disclosed. A non-real time sampling technique which makes use of the repetitive nature of the input analog signal is utilized to achieve the desired high frequency digitizing of the analog signal. Subsequent data reduction, parameter evaluation and display of test results are achieved under the control of a microprocessor-controlled subsystem. Communication with an external host system is effected by means of the IEEE-488 general purpose interface bus.