8
RS-232
↔
CURRENT LOOP INTERFACE CONVERTER
3. Configuration and Installation
The RS-232
↔
Current Loop Interface Converter is easy to use. It contains no
internal jumpers or DIP switches to set, so you’ll never have to open the case to
configure the unit. The only configuration required for operation is proper setting
of the external DCE/DTE switch.
3.1 Setting the DCE/DTE Switch
For your convenience, the Converter has an externally accessible DCE/DTE switch
(see
Figure 3-1
). If the RS-232 device connected to the Converter is a modem or
multiplexor (or is wired like one), set the switch to “DTE.” This setting causes the
Converter to behave like Data Terminal Equipment, transmitting data on RS-232
pin 2 and receiving data on pin 3.
If the RS-232 device connected to the Converter is a PC, terminal, or host
computer (or is wired like one), set the switch to “DCE.” This setting causes the
Converter to behave like Data Communications Equipment, transmitting data on
RS-232 pin 3 and receiving data on pin 2. Remember, the switch setting is always
from the point of view of the Converter, not the connected equipment.
Figure 3-1. DCE/DTE Switch Positions.
3.2 Installing the Converter
You can install the Converter in two different applications: RS-232 to
active
current
loop or RS-232 to
passive
current loop.
3.2.1 RS-232
TO
A
CTIVE
C
URRENT
L
OOP
R
UNNING
P
ASSIVE
The simplest installation of the Converter is into environments where an RS-232
device is communicating with an
active
current-loop device. In this case, both the
RS-232 and current-loop interfaces are automatically supplying power to the data
circuit. As
Figure 3-2
illustrates, only 4 wires are needed to connect the current
DTE
DCE