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14
en | Installation
4.2.3
Backup DC power supply
The VARI base unit is equipped with a backup DC power input. In the event of AC mains
failure, the internal power supply will automatically switch to this backup input, allowing the
loudspeaker to continue operation under what may be emergency conditions.
The backup DC supply will typically be from batteries, and should be 24 V.
Note that the current drawn by the VARI unit from the backup supply will be much higher than
that drawn from the AC-mains, and the cable used must have an adequate current rating.
Refer to section Backup DC power supply input (2), page 24 for wiring details.
4.2.4
Failure relay
If network monitoring is not to be used (see below), a simple surveillance function may be
realised by use of the VARI's failure relay. The failure relay connector provides both volt-free
and switched-impedance contacts, the latter suitable for impedance-sensing fault-monitoring
equipment.
Refer to section Failure relay (11), page 28 for wiring details.
4.2.5
Control input
The VARI is fitted with an external control port which can be used to load an internal
"emergency" configuration in the form of a preset from memory in the event of, e.g., network
failure.
Refer to section External control input (10), page 28 for wiring details.
4.2.6
RS-485 network
The VARI's RS‑485 connection is primarily the method by which it gets configured using the
VariControl software application. The unit's configuration file will generally be loaded before
mechanical installation, using the cable supplied with the VARI‑CS Configuration Set.
Additionally, continuous monitoring of the unit's performance and external control may be
realised via the RS‑485 connection. If this feature is to be implemented, a permanent RS‑485
network connection will need to be run to the VARI's installed location. In that case the
configuration file can just as easy be loaded after mechnical installation.
The VARI has two identical RS‑485 connectors, paralleled internally, allowing multiple VARI
units to be easily "daisy‑chained".
The type of cable necessary for correct operation of the RS‑485 network is twin twisted pair
with each pair individually shielded. Numerous cables of this type are readily available and
cables broadly meeting the specifications of the example cable given below are likely to be
suitable. Example of a preferred cable type:
Parameter
Type
Characteristic impedance
Capacitance (core to core)
Capacitance (core to screen)
DC resistance (core)
DC resistance (screen)
Refer to section RS-485 network in (8) and thru (9), page 26 for wiring details.
2018.06 | V1.3 |
Value
BELDEN 'Datalene' series No. 9729 2-pair, pairs
individually screened
100 ohms
41 pF/m
72.5 pF/m
78.7 ohms/km
59.1 ohms/km
Installation manual
VARI-directional array
Bosch Security Systems B.V.
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