Bosch Appliances Radio 420 User Manual

Fire Alarm Systems | FLM‑I 420‑S Short Circuit Isolator

The Short Circuit Isolator isolates alarm zones in which a
short circuit has occurred. This means the functionality of
the remainder of the network remains preserved.

b1+        a-       b2+      N/A     N/A    N/A

LSN 

9      1

6      4

7           3

8           2

0

5

8           2

0

5

6      4

9      1

7           3

CL      1

2

0

b1+ / a- / b2+ LSN
N/A (3 x)

free terminals, e.g. for looping through ext. auxiliary volt-

age and for shielding

Features of improved LSN
The interface modules in the 420 series offer all the
features of improved LSN technology:

•

Flexible network structures including T‑tapping

without additional elements

•

Up to 254 LSN-improved elements per loop or stub

line

•

Unshielded cable can be used

Address switch (rotary switch)
The address of the Short Circuit Isolator is set using the
rotary switches.
The following settings are possible:

0 0 0

Loop/stub in LSN mode improved version with automatic

addressing (T-tap system not possible)

0 0 1 - 254

Loop/stub/T-tap system in LSN mode improved version

with manual addressing

CL 0 0

Loop/stub in classic LSN mode

Configuration
The Short Circuit Isolator isolates alarm zones in which a
short circuit has occurred. The following illustrations
show typical configurations of the isolator module.

▶ Rotary switch for automatic and manual address

▶ Preservation of LSN loop functions in the event of a

▶ Power supply via LSN
▶ Three free screw terminals