Abstract: A production control system is provided, especially for use in a works environment, in which a microsequencer controlled by a Z80 microcomputer board (MUXC) performs continuous high-speed scanning of a multiplicity of operator input devices (OIDs) located at the work stations of individual human operatives. The microsequencer is essentially a single-level pipelined microprocessor communicating with the OIDs via channels and sub-channels, each OID being connected to a respective sub-channel by a single twisted-pair cable. The cable lines are maintained at 24 volts d.c. to supply power to the OID, and the OID, which has a card-reader for reading bar code on cards or tickets passed through it by the operative, transmits data to its sub-channel, and hence the microsequencer, over the same cable by shorting out the two cable lines for short and long pulse periods.