Abstract: An interface system for a PLATO IV computer terminal and random access slide projector that permits use of standard slides. The terminal keyboard selects a slide number which causes a strobe signal and binary signal representing the number to be transmitted to the interface. The number is latched in the interface upon reception of the strobe and then fed to a programmable read only memory (PROM) where the binary signal is algorithmically converted into a base 9 system. The output of the PROM is fed to decoders which convert the base 9 numbers into high and low order signals and are then fed to the slide projector after passing through inverter drivers and protective diodes. The interface also controls the ON/OFF position of the projector and generates an access signal to the projector after it has received the slide number in proper form.

Abstract: A resolver-to-digital converter where a signal of predetermined frequency is converted to a given waveform sequence by a logic circuit, band passed filtered, and phase splitted into orthogonal components. These components are fed to operational amplifiers and then into the input windings of a resolver. The outputs of the resolver are fed to a pair of zero crossing differential comparators and then to phase detectors, the outputs of which are summed. The sum of the signals is filtered and is used to regulate a voltage controlled oscillator that pulses a synchronous counter that is fed back to the phase detectors forming a phase-locked loop. The synchronous counter feeds a serial register that is strobed by the output of a zero crossing differential amplifier fed by the compensation windings of the resolver.