Fire-Lite LCD-80FC Remote Fire Indicator - Manual (Page 20)

20 LCD-80FC Instruction Manual — P/N 53244:B 5/13/2013
Section 5: EIA-485 Shield Termination
The EIA-485 circuit must be wired using a twisted, shielded pair cable with a characteristic imped-
ance of 120 ohms (+/- 20%). Do not run cable adjacent to or in the same conduit as 120 VAC ser-
vice, noisy electrical circuits that are powering mechanical bells or horns, audio circuits above 25
V
RMS
, motor control circuits or SCR power circuits.
5.1 Shield Not in Conduit
The EIA-485 line allows the FACP to communicate with the LCD-80FC Indicator. The shield for
the EIA-485 line must be connected to earth ground at the FACP but must be left floating (no con-
nection) at the indicator if it is the first or only device on the EIA-485 line. If a second indicator is
connected, the shield leaving the first indicator must be left floating. The shield entering the sec-
ond indicator must be connected to the three-gang box or Earth Ground terminal (P2-7) on the sec-
ond indicator. If additional indicators are connected, the shield leaving each enclosure must be left
floating and the shield entering each must be connected to the three-gang box or the Earth Ground
terminal (P2-7) on the indicator.
NOTE: To ensure static (ESD - electrostatic discharge) protection, all enclosures, including the
LCD-80FC electrical box, must be connected to earth ground! Never use the EIA-485 shield for
this purpose. The EIA-485 shield is for radiated noise emission protection (RFI, EMI). Refer to the
following figures for details on EIA-485 shield termination.
Connect the drain wire to the outside of the
FACP cabinet via a BX-type connector.
Shield Drain Wire
FACP Backbox
(+) EIA-485
(-) EIA-485
FACP
fd
u8
0sh
l.w
mf
FACP indicator
indicator indicator
Figure 5.1 EIA-485 Without Conduit
shield
EIA-485 Loop
not in conduit