AFP-400 Installation
PN
50253
:
A2 03/12/96
2-47
The total length of wire (12 AWG) in a four-wire loop cannot exceed 10,000
feet. Find the total length of wire in the loop by summing the wire lengths
on each loop. The following wiring diagram identifies the output and return
loops from SLC terminal TB5 on the CPU-400.
Wire Requirements for a Four-Wire SLC Circuit
Loop Resistance
Loop Out
Loop Return
Measuring DC Resistance of a Four-Wire SLC Loop
For detailed wiring require-
ments, refer to Appendix B.
Wiring a Four-wire SLC
Loop
T-Tapping is not
allowed on a four-wire
SLC loop.
no connection
Loop B (output
loop)
Loop A (return loop)
The total DC resistance of the communications loop pair cannot exceed
40 ohms. Measure DC resistance as follows:
1) Disconnect the Loop Out and Loop Return at the control panel.
2) Short the two leads of Communications Loop Return.
3) Measure the resistance across the Loop Out leads.
CPU-400
Four-Wire SLC Circuit Loop
