26
Device loop circuits
Device loop circuits
The two device loop circuits can each accept connection of addressable devices /
outstations, up to 200 maximum per circuit. To maintain earth continuity on a loop, the
loop cable screen must be continued through each system device, whether the earth is
connected to a device or not.
A loop circuit must not cover more than 10,000m
2
of fl oor area of a
protected site.
A spur circuit must always be taken from the ‘line common’ terminals
of a 3 ways device.
A spur must not cover more than the equivalent of one zone as
defi ned in BS 5839 Part 1.
As every device has a loop isolator, the application of more than
32 devices does not require any special consideration.
L1
01
L2
02
Manual call point
0V
C
L1
0V
3
4
IN 1
OUT 2
L2
L2
02
S device
(2-way)
3
01
L1
02
L2
01
L1
PANEL
S-Quad
S device
(2-way)
3
Earth to
metal box
Master Control Board
LOOP CIRCUIT 1
L1 0V L2 0V
LOOP n
IN4
OUT5
C3
S-Quad
IN4
OUT5
C3
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