Blind plate 05701-A-0365

5704 Gas Card and Catalytic Type Detector

Catalytic detectors require a three wire connection and the detector documentation will

indicate three connections S, 01 and NS, which are usually brown, white and blue

respectively.   At the System 57 end of the field cable, the three detector wires should each be

connected to the respective matching S, 01 or NS terminal of the appropriate channel on the

Quad Relay Interface Card that is attached to the required Four Channel Control Card.

5704 Gas Card and 2 Wire Loop Powered Detectors

Loop powered detectors require a two wire connection and the documentation will indicate

the positive and negative loop connections, usually brown and blue respectively.

At the System 57 end of the field cable the two detector wires should be connected to the S

(positive) and 01 (negative) terminals of the appropriate channel on the Quad Relay

Interface Card that is attached to the required Four Channel Control Card.

5704 Gas Card and 3 Wire 4-20mA Transmitter

ctor documentation

Transmitters require either three or four wire connections and the dete

will indicate the 0V and +24V power connections and the positive and negative loop

connections. At the System 57 end of the field cable the detector loop signal wires sh

connected to the S, 01. NS terminals on the Quad Relay Interface Card that is attached to

the required Four Channel Control Card. The exact terminals used vary depending upon

whether three or four wire topology is used, the requirement for a loop current source

configuration and the channel to be connected to. The transmitter power connection +2

and 0V should be connected to a suitable dc supply.

ould be

4V

ote: Terminals 35 and 36 on the Relay Interface Card are input terminals only and cannot

N

be used to power the transmitter.

he Schematic below details the connections for 3 wire current source transmitters. For

T

other schematics (including isolated and barrier) refer to operating manual 05704-M-5001

5704 Fire Card

The 5704F fire input circuit operates from the system dc input supply (21 to 32V) but has a

built-in voltage limiter that limits the maximum loop voltage to +24V to protect the detectors

from damage. When the system supply is less than +24V the limiter has no effect and the

loop will see the true input supply voltage. The loop current is determined by measuring the

voltage across a 220 ohm current sense resistance. A link selectable 330 ohm barrier

equivalent resistance is incorporated for use when an external IS barrier is NOT fitted. For

fault monitoring purposes, an end of line (EOL) resistor must be fitted in or after the last

detector on the loop. The typical value for the end of line resistance is 5.1k ohms although

this may need to be reduced when many detectors are fitted onto the loop.

An equivalent circuit of one fire input together with an example detector connection is shown

below:-

Line Resistance

Detectors should be located such that the line resistance of the cable required does not

prevent correct operation. As a general guide and for a typical installation of twenty low

quiescent current detectors, the loop cable resistance should be kept below 100 ohms total

(50 ohms per core). The table below gives a quick guide to the maximum cable lengths

permitted in this case: