Wiring a Signaling Line Circuit (SLC) Installation
IQ-301 PN 50036:F 10/29/2001 45
2.9.7 Wire Requirements for a Two-wire SLC
Measuring Loop Resistance for a Two-wire SLC
The total DC resistance from panel to branch end cannot exceed 40 ohms. Measure DC
resistance as shown in Figure 23:
Figure 23 Measuring DC Resistance of a Two-wire SLC
1. Short the termination point of one branch at a time. Measure the DC resistance
from the beginning of the loop to the end of that particular branch.
2. Repeat this procedure for all remaining branches in the SLC.
Measuring Total Wire Length for a Two-wire SLC
The total length of wire (12 AWG) in a two-wire SLC cannot exceed 10,000 feet (3048
m). Find the total length of wire in the SLC by summing the wire lengths on each
branch of the SLC. Figure 24 shows how to find the total length wire in a typical
two-wire SLC.
CAUTION: Terminate shield drain wire according to the instructions in “SLC
Shield Termination” on page 43.
Figure 24 Measuring the Total Length of Wire in a Two-wire SLC
For detailed wiring
requirements, refer
to Appendix F.
SLC Out
Branch
!
(Branch A)
+(Branch B)
+(Branch C)
+(Branch D)
+ (Branch E)
=10,000 feet (3048 m) or less
(12 AWG)
Branch B
Branch E
Branch C
Branch D
Loop Out Branch A
no connection
CPU
TB6
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