NEC DTU-70 Instruction Manual page 73

3-7-4-2 Serial Communication Interface
The connection of the serial communication interface with the remote control
equipment is made by means of a connector of the interface board. The serial
communication interface has a function to output data displayed on the LCD
display. The method of setting and specifications related to serial communications
are described below.
(1) Setting of hardware
1) Setting of jumpers
Jumpers on the control board in the TX control unit are set as follows.
For positions of jumpers on the control board, see Fig. 3-10.
a) JS507, JS510, JS511, JS512, JS513, JS514, JS515
1-2 : RS-232C
2-3 : RS-422/485
b) JS508, JS509
1-2 : RS-422/485 with termination
3-4 : RS-422/485 without termination
Note : Usually RS-422 is set to condition with termination.
3 - 25
GWP-G22996