Bidirectional logic analyser for digital electronic signals

A logic analyser for electronic signals in digital applications is able to operate independently of the signal direction by the use of serial switching through a polarity dependent transistor which constitutes the switching element. This is connected in series with a diode and the resistance of the supply voltage. The switching element is controlled by the signal source. An antiparallel switching series, also controlled by the signal source, transmits signals in the opposite direction. The system can be adapted for use with high-strength signals, e.g. TTL or CMOS, by applying a constant current to the resistors so that only the maximal current is admitted. Thus the same logic analyser can be used irrespective of loading.