<P> The PS / 2 port is a 6 - pin mini-DIN connector used for connecting keyboards and mice to a PC compatible computer system . Its name comes from the IBM Personal System / 2 series of personal computers, with which it was introduced in 1987 . The PS / 2 mouse connector generally replaced the older DE-9 RS - 232 "serial mouse" connector, while the PS / 2 keyboard connector replaced the larger 5 - pin / 180 ° DIN connector used in the IBM PC / AT design . The PS / 2 designs on keyboard and mouse interfaces are electrically similar and employ the same communication protocol . However, unlike the otherwise similar Apple Desktop Bus connector used by Apple, a given system's keyboard and mouse port may not be interchangeable since the two devices use a different set of commands . </P> <P> Communication is serial, synchronous and bidirectional . The attached device generates the clock signal . The host controls communication using the clock line; when the host pulls the clock low, communication from the device is inhibited . </P> <P> Older laptops and most contemporary motherboards have a single port that supports either a keyboard or a mouse . Sometimes the port also allows one of the devices to be connected to the two normally unused pins in the connector to allow both to be connected at once through a special splitter cable . This configuration is common on IBM / Lenovo Thinkpad notebooks among many others . </P> <P> The PS / 2 keyboard interface was electrically the same as for the 5 - pin DIN connector on former AT keyboards, and keyboards designed for one can be connected to the other with a simple wiring adapter . In contrast to this, the PS / 2 mouse interface is substantially different from RS - 232 (which was generally used for mice on PCs without PS / 2 ports), but nonetheless many mice were made that could operate on both with a simple passive wiring adapter, where the mice would detect the presence of the adapter due to its wiring and then switch protocols accordingly . </P>

Ps/2 keyboard/mouse combo port