An interface to input analog signals to a remotely located computer

Two simple components are described that allow a single microprocessor to monitor several analog instruments. A remote control box with a speaker and a switch allows communication between the operator and the microprocessor. Amplifiers on a printed circuit board ensure that there is no loss in resolution of the input signal. The circuitry allows offset of the input signals relative to the electrical zero, adjustment of the gain of each amplifier and, most importantly, protects the analog to digital converter against destruction by over-range voltages.