System calculations
EST3 Installation and Service Manual B.5
Signature data circuit wire length
Circuit resistance and capacitance determines the maximum
length of a Signature data 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 Signature data circuit must not exceed either of
the two measurements.
There are no restrictions placed on the wiring used for the
Signature data circuit. Longer wire runs may be obtained using
standard (non-twisted, non-shielded) wire pairs.
Determining the maximum allowable branch
length
The maximum branch length is the wire distance measured from
the Signature controller module to the last device on the longest
circuit path as shown below.
Signature
Controller Module
10 12
5
1
6
[WIRECALC2.CDR]
Several factors influence the maximum allowable branch length:
• Wire gauge and type
• Number of Signature detectors and modules installed on the
branch
• Number of SIGA-UMs configured for 2-wire smoke
detectors installed on the branch
Table B-1 through Table B-3 provide the maximum allowable
branch length for any detector, module, SIGA-UM, and wire
gauge combination. Using the wire distances specified in the
tables ensures that the circuit does not exceed the maximum
circuit resistance of the Signature data circuit.
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