Serial mouse

Pin  Description
 1   DCD   Data carried detect
 2   RD    Receive data
 3   TD    Transmit data
 4   DTR   Data terminal ready
 5   SG    Signal ground
 6   DSR   Data set ready
 7   RTS   Request to send
 8   CTS   Clear to send
 9   Ring

eg: Serial control for NEC projectors LT240,260,245,265.....and others.

This is the "standard" Mac serial din-8 out pinout.