The Parallel Port Interface (PPI) units provide quick and easy interfacing to the PC by connecting a cable to the parallel port. This method of connection reduces the initial set-up time, eliminates the requirement to open up the PC and increases the flexibility of the unit by enabling it to be moved easily between PCs. This provides a quick and easy method of connecting TTL devices to a PC. The PPI1 is designed for interfacing with TTL 5v devices and includes one analogue 8-bit 0-5v input. The Parallel Port Interfaces have been designed so that they can be used with almost any programming language, for example, Visual BASIC, Delphi and C and also National Instruments LabVIEW. Also included are drivers and sample programs.