A secure serial communication gateway device (11, 52) comprising: at least one first serial communication host connector to connect to at least one first host computer; a serial communication peripheral device port (A, B) to connect to a peripheral device; and a security circuitry comprising: a pre-qualification microcontroller (32a, 32ab, 32d); a mode select switch (9dm, 9dp) connected to said serial communication peripheral device port and selectively connecting said serial communication peripheral device port to the selected one of: said pre-qualification microcontroller (32a, 32ab, 32d); and said first serial communication host connector; and a serial communication enumeration and reset detector, connected to said serial communication peripheral device port (A, B), to monitor said serial communication peripheral device port and causing said mode select switch (9dm, 9dp) to switch said serial communication peripheral device port to said pre-qualification microcontroller (32a, 32ab, 32d) when said serial communication device is disconnected from said serial communication peripheral device port; characterized in that said pre-qualification microcontroller (32a, 32ab, 32d) is capable of enumerating a connected peripheral device according to a table of peripheral device qualifications, said table of peripheral device qualifications may be field re-programmed, and the security circuitry is housed within said peripheral device port (A, B). at least one first serial communication host connector to connect to at least one first host computer; a serial communication peripheral device port (A, B) to connect to a peripheral device; and a security circuitry comprising: a pre-qualification microcontroller (32a, 32ab, 32d); a mode select switch (9dm, 9dp) connected to said serial communication peripheral device port and selectively connecting said serial communication peripheral device port to the selected one of: said pre-qualification microcontroller (32a, 32ab, 32d); and said first serial communication host connector; and a serial communication enumeration and reset detector, connected to said serial communication peripheral device port (A, B), to monitor said serial communication peripheral device port and causing said mode select switch (9dm, 9dp) to switch said serial communication peripheral device port to said pre-qualification microcontroller (32a, 32ab, 32d) when said serial communication device is disconnected from said serial communication peripheral device port; a pre-qualification microcontroller (32a, 32ab, 32d); a mode select switch (9dm, 9dp) connected to said serial communication peripheral device port and selectively connecting said serial communication peripheral device port to the selected one of: said pre-qualification microcontroller (32a, 32ab, 32d); and said first serial communication host connector; and said pre-qualification microcontroller (32a, 32ab, 32d); and said first serial communication host connector; and a serial communication enumeration and reset detector, connected to said serial communication peripheral device port (A, B), to monitor said serial communication peripheral device port and causing said mode select switch (9dm, 9dp) to switch said serial communication peripheral device port to said pre-qualification microcontroller (32a, 32ab, 32d) when said serial communication device is disconnected from said serial communication peripheral device port; characterized in that said pre-qualification microcontroller (32a, 32ab, 32d) is capable of enumerating a connected peripheral device according to a table of peripheral device qualifications, said table of peripheral device qualifications may be field re-programmed, and the security circuitry is housed within said peripheral device port (A, B).