Black Box ME540A-ST, Manual, Page: 14 / 26

FOM LINE DRIVER—ST AND S M
1 3
4.4 20-mA Current Loop (Point to Point)
NOTE
To use the following switch positions appropriately, you should have a firm understanding
of your network requirements.
1.
Connect the wire to the terminal block.
Set the wire to TB1 (the 4-wire terminal block) as indicated
below for 4-wire current-loop applications:
Position 1 ------Receive B positive (+)
Position 2 ------Receive A negative (-)
Position 3 ------Transmit B positive (+)
Position 4 ------Transmit A negative (-)
2.
Set S5.
Move S5 to the Current Loop position, A. S5 determines which circuit is tied to TB1.
3.
Set S2 and S3.
To configure the current loop transmitter and/or receiver as active or passive, set S2
and S3 as shown below.
S2—20-mA Current-Loop Receive
A --------Active
B --------Passive
S3—20-mA Current-Loop Transmit
A --------Active
B --------Passive