The reed switch sensor can be used to detect the presence of a magnetic field such as from a bar magnet or an electromagnet. Alternatively, a simple external switch can be wired to the internal screw terminals. It has a fast response time of 2 ms so can be used as an alternative to a light gate for timing applications. Other uses include monitoring the amount of time a door is left open or a machine running. This is used both in the DrDaq and the EL001 triple channel converter.