Plena Voice Alarm System Installation | en 43
Bosch Security Systems B.V. Installation and Operation manual 9922 141 1037x (V2.16) | V0.6 | 2011.09
4.9 Dummy load
To install the Dummy load do as follows:
1. Connect the two leads onto the connection terminals of the last loudspeaker in a line.
2. Attach the Dummy Load circuit board in the loudspeaker cabinet to the mounting studs.
4.9.1 Set the jumper JP1 on the Dummy load
The Dummy Load has these functions:
– Increases the percentage of impedance (with respect to the cable impedance) present at
the end of the line.
– Allows more loudspeakers to be fitted.
– Allows longer cable lengths.
Fault detection of the loudspeaker lines with impedance measurement is triggered by a
change in excess of 20%. The impedance at the end of the loudspeaker line must be more
than 20% of the total impedance to make sure that an open circuit is detected.
The Dummy Load has a jumper to set the load at 20 kHz to 8, 20 and 60 W.
1. Use the Dummy Load Calculator to calculate the jumper setting of JP1 on the Dummy
load.
2. Select the Excel sheet Dummyload calculator. Click on Enable Macros when the dialog
box appears. The worksheet opens.
3. Type the load per loudspeaker in Step 1. The maximum number of loudspeakers is
automatically calculated and appears in Step 2.
4. Type the number of loudspeakers in the line in Step 2. The result automatically appears
in Step 3.
5. Type the capacitance of the 100 V cable in Step 4.
6. Type the length of the cable in Step 5.
7. Click Display jumper JP1 settings. The configuration of the jumper settings appears.
8. Set the jumper JP1 on the Dummy load to the shown in the calculator.
NOTICE!
In some loudspeakers only one mounting stud is available as the studs are too far apart.
NOTICE!
You can find the Dummy load calculator.xls on the Plena Voice Alarm CD.
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