The PIO-D56/PIO-D24 provides 56/24 TTL digital I/O lines. The PIO-D56 consists of one 24-bit bi-directional port, one 16-bit input port and one 16-bit output port. However, PIO-D24 only contains the 24-bit bi-directional port. The 24-bit port supports three 8-bit groups, which are PA, PB and PC, respectively. Each 8-bit group can be individually configured to function as digital input or output port. Each group in a 24-bit bi-directional port is configured as digital inputs once the power is turned on or if a reset has been executed. DB-24PD is the daughter board, which is designed to connect the input port for either isolation purposes or to interface to the output port for relay control. PIO-D24 has one D-sub connector. However, The PIO-D56 contains one D-sub connector and two 20-pin flat cables. The flat cable can be connected to an ADP-20/PCI adapter. The adapter can be fixed onto the chassis. This product can be installed into a 5V PCI bus and supports actual “Plug & Play” technology.