The block diagram is pretty self explanatory. Various types of sensors
produce various analog voltages which are shifted and amplified using op-amps in
the signal conditioning circuits. The analog multiplexer selects one of these
analog voltages and connects it to the A/D converter. The A/D converter
digitizes this analog voltage and passes it on to the PC via the parallel port.
A photograph on the next page shows the circuit with its relevant portions demarcated and labelled according to their functions.