Ma Current Loop - UBI EasyCoder 501 Service Manual

UBI EasyCoder 501 – Service Manual
18. "UART1:", cont'd.
18.4

20 mA Current Loop,

cont'd.
The examples below illustrate two of four possible cases of the
printer or host computer being active transmitter or receiver, i.e.
being the supplier of the current to the loop.
PRINTER
Printer active transmitter/active receiver
+
TXD+
Transmitter
Pin 12
-
+
Receiver RXD+
47 ohm
RXD-
-
Printer active transmitter/passive receiver
+
TXD+
Transmitter
TXD-
-
Receiver
RXD+
47 ohm
RXD-
CABLE
Pin 9
Pin 11
TXD-
Pin 10
Pin 13
Pin 18
Pin 25
Pin 14
Pin 9
Pin 11
Pin 12
Pin 10
Pin 18
Pin 25
COMPUTER
+
-
142