Epson C82305 - Manual (Page 24)

RECOMMENDED CIRCUIT CONNECTIONS
Recommended line driver and line receiver for RS-232D
signal level settings. (As viewed from the host computer.)
Figure 4. RS-232D
Line Receiver
Serial Interface Card
Recommended line interface circuit for 20mA Current
Loop signal level settings. (As viewed from the host
computer.)
Figure 5. Current Loop
Note
The value of "R" should be selected so that the loop
current is set between 10 and 20 mA. The "+v" should
be 3V to 24V.
21