Bosch Security Systems | 2006-06 | 9922 141 10377 en
Plena Voice Alarm System | Installation and User Instructions | Equipment en | 67
14 End of line detection
14.1 Introduction
The End Of Line (EOL) detection board makes a
continuos check of the integrity of the loudspeaker line
based on a pilot tone. This check is in addition to the
check given by the impedance measurement. The pilot
tone is independent of the quantity of the loudspeakers
in the system or the load on the speaker cables.
14.2 Overview
The EOL is installed in the speaker cabinet at the
furthest point on a loudspeaker line. When the EOL
detects a pilot tone that is given by the voice alarm
system, the loudspeaker lines have no fault. The EOL
trigger output is closed and the LED lights up to show
that the lines have a pilot tone signal.
If the loudspeaker cable has a fault, the pilot tone stops.
The EOL circuit becomes open, which is detected by
the Voice Alarm Controller.
One EOL board can be installed to give a single fault
indication per zone or more than one can be installed
on a single fault input to check the integrity of a
loudspeaker line with several branches. When more
than one EOL board is installed, the configuration is
called a daisy-chain.
When a fault is detected by the VAC, to find the EOL
board that detects the failure, every individual board
must be checked.
14.3 Installation
To install an EOL, use these general notes.
• An EOL board can only be installed in a
2-channel system. The EOL board needs the sec-
ond amplifier to produce the pilot tone for the
zones that are not in use. Refer to 17.5.3.
• The volume control on the VAC must be set to
-9 dB or higher. The recommended setting is
0 dB. A lower dB setting attenuates the pilot tone.
• All inputs to a VAC or router that have an EOL
input must be normally closed inputs. The EOL
board operates with a normally closed output and
the configuration software is set to
Action Open
.
Use another router to receive normally open inputs.
• The Short circuit check must be set in the config-
uration software.
Note
Do not connect the EOL board to the
secondary side of a volume control.
The secondary side of a volume control can
attenuate the pilot tone.
Note
During a call the pilot tone is absent in zones
without a call or without background music. The
red LED on the EOL board is dim. The EOL input
is ignored during calls to avoid false fault readings.
Note
The EOL board detects a short circuit, but the
EOL cannot detect where the short circuit is.
Note
It is possible for the LED will to turn off before
the contact is opened or vice versa. This level
difference is typically less that 500 mV.
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