900 Series V5.1: Installation Guide, February 2000 7
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According to the EN54 directive, isolators must be placed at least every 32
devices.
3.1.1.3. Isolator base for 950/990 Series monitors - DB960/DB961
An isolator base comprises of a Series 950 addressable mounting base fitted with a
printed circuit module for sensing and isolating a short-circuit between the conductors
supplying power and the communications signals to the base. Mounted on the side of the
base is a yellow LED that lights up when there is a short-circuit condition. There is a five-
way terminal block with rising clamp connectors to terminate supply conductors.
There are nine terminals on the base:
L1 OUT: Line out, four terminals (Positive and negative loop supply)
L2 IN: Line in, three terminals (Positive and negative loop supply)
+R: Remote indicator (LED) positive supply, one terminal
-R: Remote indicator (LED) negative supply, one terminal
Isolator bases are polarity sensitive and can be damaged if connected to a reverse
polarity supply capable that can deliver in excess of 1 amp. Observe the polarity
markings indicated behind each supply terminal.
Figure 3: Wiring diagram for DB960/DB961
À Isolating base  Typical loop wiring Ä Control panel loop
driver
Á Series 950 base à Typical spur wiring
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According to the EN54-directive isolators must be placed at least every 32
devices.
3.1.1.4. Relay base for 950/990 Series monitors – DB950R
The DB950R relay base features a set of volt-free, form C (change-over) contacts
controlled and powered by the remote output of an Series 950 or 990 detector. Low
power operation and a high maximum operating frequency are achieved by using a
latching relay coupled to an efficient drive circuit. The facility to drive a remote LED is
retained by auxiliary output that mimics the detector's remote output.
Typical spur
wiring
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