This unit is designed to assist in the understanding of digital and analogue communications systems. When a variable voltage is applied to the input terminals it is converted into a digital output. One volt input corresponds to binary 1, 2 volts for binary 10, 3 volts for binary 11 etc. up to 7 volts binary 111. There is a fine setting as well with 2V corresponding to binary 111. A low frequency AC input signal can be converted into a changing digital value. Use on its own or combined with the DAC to decode back into a stepped analogue voltage. The unit requires a plugtop 12V PSU - available separately or may be powered from the front panel sockets using a good 12V DC power supply.