Fire-Lite ECC-FFT Firefighters Telephone - Manual (Page 18)

18 ECC-FFT Instruction Manual — P/N LS10031-000FL-E:B 9/4/2013
Installation SLC Device Installation
Figure 2.8 and Figure 2.9 show how length is determined for out and return style wiring.
When using T-taps, the total length of all taps and the main bus must not exceed 40,000 feet. This
requirement must be met in addition to the maximum distance requirements for the various wire
gauges.
Figure 2.8 Calculating Wire Run Length
The dotted line path shows how the
wire distance is calculated for the
SLC device at the end of the run.
The wire distance must be less than
the maximum per wire gauge.
SLC device
SLC device
SLC device
SLC device max loop resistance = 40 ohms
SLC Circuit
Figure 2.9 Calculating Wire Run Length for a T-tap
In this example:
= 1000 feet
= 1600 feet
= 3500 feet
16 AWG wire can be used
because the greatest distance is
3500 feet
The device located farthest from
the SLC must be less than the
maximum distance per wire gauge.
SLC device
SLC device
SLC device
SLC device max loop resistance = 40 ohms
SLC Circuit