NEC NP4001 - Manual (Page 141)

8. Specifications
129
Note:
Depending on the equipment, a lower baud rate may be recommended for long
cable runs.
PC Control Connector (DIN-9P)
Note:
1. Pin 1, 4, 6 and 9 are not used.
2. Jumper “Request to Send” and “Clear to Send” together on both ends of the
cable to simplify the cable connection.
3. For long cables, it is recommended to set communication speed within projector
menus to 9600 bps.