Rockwell Automation T8847 Trusted 40 Channel Fire Input Versatile FTA - Manual (Page 7)

Trusted
TM
Fire Input Versatile FTA T8847
Issue 4 Sep 05 PD-T8847 7
1. Description
The Trusted TM 40 Channel Fire Input Versatile FTA T8847 provides termination for a maximum of 40
input channels from various types of field devices associated with the detection of fire hazards. These
include smoke and heat detectors, and manual alarm callpoints (MACs) etc. The 40 channels are
arranged in five power groups each comprising eight identical channels. Figure 2 below shows the
configuration of a single channel within a group.
Figure 2 Single Channel Schematic
Each power group is supplied from dual 24V dc feeds which are ‘commoned’ via diodes on the VFTA.
The supply is then fed to each channel within the group
The supply voltage to the field is fed via the 315mA fuse. The incoming signal from the field device is
fed through the 315mA fuse which effectively limits the input signal. The voltage developed across the
560R resistor is used by the input module to detect the field device status.
Note: This VFTA is suitable for use with MTL 5061 I.S barriers in instances where the field device is
located in hazardous areas of the plant.
The cable linking the 40 channels on the input module to the VFTA is terminated at five 10-way
connectors (TBG1 to TBG5). SmartSlot signals from the module are connected to a single 7-way
connector (TBGSS). The dual 24V dc power supplies are connected to the VFTA via five 4-way
connectors (TBFP1 to TBFP5). Forty 3-way connectors are used for the field loops (TB1 to TB40).