Bosch PRAESENSA Manual page 53

PRAESENSA
4.
Single Class A wiring (A to B)
Figure 3.9: Single Class A wiring
A third loudspeaker connection topology is the so-called Class‑A loop, where the loudspeakers
are connected in a loop, starting at output A and ending at output B, with the end of the loop
being supervised with an end‑of‑line device.
Follow the procedure below to connect the loudspeakers according to this scheme:
1.
2.
3.
Output fault detection
Output fault detection can be tested with the following means:
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Bosch Security Systems B.V.
Connect an end-of-line device to the end of loudspeaker line B. Loudspeaker lines A and
B must be separately supervised, each with its own end-of-line device. In case of a short
circuit in one of the loudspeaker lines, the amplifier will diagnose the overload condition
to find the affected loudspeaker line and switch‑off that line, so the other loudspeaker
line can continue operation.
(EOL-US)
Connect all loudspeaker in parallel in a loop‑through fashion. Observe equal polarity for
all loudspeakers. Connect one side of the loudspeaker cable to output A, observing
polarity.
Connect the other side of the loudspeaker cable to output B. In this case maintaining the
correct polarity is especially important, as reversal on one end will short circuit the
amplifier channel, not immediately, but when output B is activated in case of interruption
of one conductor.
Connect an end‑of‑line device to output B, in parallel with the loudspeaker cable.
Ground short detection: Connect between one of the output conductors, of one of the
loudspeaker outputs and safety ground, a 50 kohm resistor.
Short circuit: Connect a ≤ 500 mohm resistor between the plus and minus of output A or
output B, of one of the loudspeaker outputs.
Open circuit: Unplug one of the loudspeaker output connectors.
Underwriters Laboratories Listing Document (ULLD)
Installation wiring | en
2021.12.21 | V0.15b | F.01U.402.882
53