ADT Security Services ADT-LCD40 - Manual (Page 27)

EIA-485 Shield Termination EIA-485 Shield in Full Conduit
27 Document 50520 Rev D 7/25/00 P/N 50520:D
5.2 EIA-485 Shield in Full Conduit
The EIA-485 line allows the FACP to communicate with the
ADT-LCD40 Series Annunciators. The shield for the EIA-485 line
must be connected to earth ground at the FACP (both exiting and
entering the FACP) but must be left floating (no connection) at the
annunciator if it is the first or only device on the EIA-485 line. If a
second annunciator is connected, the shield leaving the first annunciator
must be floating. The shield entering the second annunciator must be
connected to the Earth Ground terminal (P2-7) on the second annuncia-
tor. If additional annunciators are connected, the shield leaving each
annunciator must be left floating and the shield entering the following
unit must be connected to the Earth Ground terminal (P2-7) on the
annunciator.
Caution! Do not allow the floating (no connection) end of the shield to
contact the conduit. The floating end should be insulated from earth
ground.
Figure 5-2: EIA-485 In Conduit
ADT-LCD40 Series Box
ADT-LCD40 Series
P1-2 (+)
EIA-485 (IN)
P1-4 (-)
EIA-485 (IN)
P2-7 Earth
Ground (IN)
Connect the shield drain wire to the Earth
Ground Terminal on the ADT-LCD40 Series
Annunciator
Shield Drain Wire
Notes:
1) Power-limited 24 VDC power may be run in the same conduit as the EIA-485 wiring
2) Twisted, shielded wire is recommended for the EIA-485 communications loop
3) Each ADT-LCD40 Series electrical backbox is connected to earth ground via the conduit
4) Shield is connected to the FACP cabinet (earth ground) leaving and entering the FACP