Then there is the GLink-LT, user port RS-232 (VIC-1011a clone) for Commodore 8-bit computers, like the VIC-20, C64, and C128. With the GLink-LT, it is usable up to 2400 baud or can be reconfigured for up to 9600 baud.
It should also work on the plus 4, as the internal 6551 is hooked up to the appropriate user port pins. Commodore obviously designed the plus 4 user port only for using a vic-1011a making it incompatible with things like "4 port" joystick adapters.
