At one time or another many readers may have thought about controlling or monitoring equipment using their PC. Electronics projects using a PC need not be lavish or expensive: often the interfaces provided on the PC can be used directly. In this series of articles we present a range of projects using the serial (RS232) port, controlled using simple programs written in Visual Basic.Why have we chosen to use the serial port, when it is more complicated and offers fewer connections than the printer port? For a beginners’ course using the serial port has several advantages:- The serial port is well protected against accidental damage. Cables can safely be plugged in while the computer is on.- There is usually a spare serial port which can be used for experiments.- The serial port can deliver enough current to power a wide range of projects, and so a separate power supply is not required.