This is a very ODD switch box, it allows one non usb computer with standard LPT DB-25 port to connect into a Standard LPT port Printer with DB 25-port, but on the B port it converts a NONE LPT port to a standard LPT-DB-25 port from a computer that has no LPT DB-25 Ports! Please see image if you are confused (like we are)
Two-Way printer switch. Manual. Also called A-B data switch. Parallel port.