A range of 25-way data switch boxes that can be used to connect a range of serial & parallel devices & computers. The units are available in two versions 2-to-1 & 4-to-1. All connectors are 25-way D-type female sockets. Generally 25-way male-female cables are used to connect to serial ports on computers male-male cables are used to connect to parallel ports for printers. Parallel printers can be connected using standard parallel printer cables. Devices requiring null-modem connections can be connected with standard null-modem cables. Modems can be connected using 25-way male-male serial cables. Other permutations are possible the boxes can also be used as 1-to-2 switch boxes.