10 900 Series V5.0: Installation Guide, April 1999
ADDR 1234567 ADDR 1234567 ADDR 1234567
36 0010010 78 0111001 120 0001111
37 1010010 79 1111001 121 1001111
38 0110010 80 0000101 122 0101111
39 1110010 81 1000101 123 1101111
40 0001010 82 0100101 124 0011111
41 1001010 83 1100101 125 1011111
42 0101010 84 0010101 126 0111111
3.2.1. Loop powered beam detector - FD950
The Series 950 beam detector is designed to protect large open spaces such as atria,
museums, churches, warehouses and factories. It has three main parts:
• The transmitter, which projects a beam of infrared light.
• The receiver, which registers the light and produces an electrical signal.
• The interface, which processes the signal and generates alarm or fault signals.
The transmitter and receiver are designed to be fitted on opposite walls approximately
30 cm to 60 cm below the ceiling. They can protect areas up to 100 m long and 15 m
wide, a total of 1500 m². If it is difficult to fit the transmitter and the receiver to opposite
walls, they can be fitted in retro mode, i.e., adjacent to each other on the same wall. A
reflector needs to be fitted to the opposite wall to reflect the beam from the transmitter to
the receiver.
The interface contains the electronic circuitry to control the beam detector and
communicate with the control panel via the Series 950 loop.
In clear air the receiver registers all the light sent by the transmitter. If smoke from an
incipient fire is present, it rises and obscures the light to a certain extent. The decrease in
the amount of light registered by the receiver causes the beam detector to change to the
alarm state.
The detector compensates for signal drift and, if the limit of compensation has been
reached, a fault signal is generated. The detector can be optionally set to return a fault if
the beam is totally and suddenly obscured.
The Series 950 beam detector has the following features:
Loop powered: The detector is loop-powered and needs no separate
24 V supply. This not only eliminates the need for
additional equipment, it also saves both cost and time in
installation.
Compatibility: It operates as a conventional detector in that it changes
to the alarm state at a pre-set level of smoke obscuration,
and can communicate with the control panel and return
information when interrogated.
Selectable alarm levels: The detector has four levels of obscuration, determined
with reference to the environment in which it is installed:
25%, 35%, 50% and 65%, where 25% is the most
sensitive and 65% the least sensitive level. A DIL switch
on the interface is used to set the obscuration level.
Drift compensation: The amount of light registered by the receiver can be
decreased by factors other than incipient fires, such as
contamination of the receiver lens. To minimise the risk
of unwanted alarms, the detector checks its status at
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