Section One; Introduction; Isolated System With Remote Supplies - Pittway Notifier RPT-485W Manual

Section One:

Introduction

The RPT-485W/RPT-485WF ACS annunciator loop repeaters are designed to boost the EIA-485 annunciator
signal from the fire alarm control panel (FACP). The RPT-485W is a repeater which supports twisted pair wire only;
the RPT-485WF supports fiber optic cable between two repeaters. Any Notifier FACP that has an EIA-485
annunciator loop can employ RPT-485s. The boosted branch can have a maximum of 32 EIA-485 devices on it.
These EIA-485 devices include AMG-1, AMG-E, UZC-256, NIB-96, ACM-16AT, all annunciators and other RPT-
485s. Note there is a maximum of two RPT-485s that can be connected in series.
The source EIA-485 circuit in a Notifier Control Panel will support up to 32 devices and up to 32 addresses along
a 6000 ft. (maximum) loop. Each RPT-485 can be employed to boost the distance of the circuit and/or add up to
32 additional EIA-485 devices (but not addresses) in the system. Figure 1.1 illustrates an electrically isolated
system. Electrical isolation is maintained by employing separate power supplies for the source and boosted EIA-
485 loops.
To remain isolated, connections between each EIA-485 device must have a reference wire from the power supply
providing power to each device. This reference wire reduces the amount of noise on the communication wire. Both
the source and boosted EIA-485 loop connection terminals are isolated from each other. These wires connect to
REF A on TB1 and REF B on TB2. In order to maintain electrical isolation between separate system power
supplies, REF A and REF B must be connected using a separate wire.
The source and boosted EIA-485 loops are isolated from each other, as well as from the RPT-485 power supply
terminals. This important feature eliminates the need to interconnect power supplies. This feature also provides
an easier method of locating ground fault conditions since it allows for separate ground fault zones. The isolation
feature does not eliminate the need for reference connections between nodes on each isolated loop. The isolation
feature will maintain isolation when networking slaves on an EIA-485 loop with the use of a NIB-96.
Figure 1-1: Isolated System with Remote Supplies
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Document 15640 Rev B1 08/13/97 P/N 15640:B1
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