Appendix A: System calculations
170 P/N 3101890-EN • REV 006 • ISS 21JUN18
Signaling line circuit wire length
Circuit resistance and capacitance determines the maximum length of a signaling line circuit. Circuit resistance
affects the wire length of the longest circuit branch. Circuit capacitance affects the total amount of wire that can be
used on the circuit.
Notes
• The design of the signaling line circuit must not exceed either of the two measurements.
• There are no restrictions placed on the wiring used for the signaling line circuit. Longer wire runs may be
obtained using standard (non-twisted, non-shielded) wire pairs.
Determine the maximum allowable branch length
The maximum branch length is the wire distance measured from the loop controller to the last device on the
longest circuit path as shown below.
(1) Loop controller
Several factors influence the maximum allowable branch length:
• Wire gauge and type
• Number of GSA detectors and modules installed on the branch
• Number of GSA-UMs or GSA-MABs configured for two-wire smoke detectors installed on the branch
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