Bosch D296 - Page 7

Long-range beam smoke detectors System overview | en 7
Bosch Security Systems, Inc. Installation manual 2017.03 | 7.0 | F.01U.068.899
Figure2.2: Beam Obscuration
1 Transmitter 3 Obscuring matter
2 Beam 4 Receiver
If an object blocks the beam, the signal falls below the trouble threshold. If this condition
lasts for more than 20seconds, the receiver signals a trouble condition. See the following
figure.
Figure2.3: Beam Blockage
1 Transmitter 3 Blocking object
2 Beam 4 Receiver
The receiver automatically compensates for gradual signal loss from dust and dirt buildup on
the cover. After a signal loss of 50%, the receiver indicates a trouble. When built‑up dust and
dirt or a blockage is removed, the detector automatically returns to normal operation level.
The receiver indicates a trouble if the beam strength increases by more than 20% for longer
than 20sec. A trouble can be caused by an initial misalignment or the removal of a partial
beam blockage during alignment. Perform a fine‑tune alignment.
For alignment details, see Setup, page 20.