Bosch PRAESENSA, Installation Manual

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38 en | System composition PRAESENSA
2019.11 | V1.00 | Installation manual Bosch Security Systems B.V.
PRA-CSLD | PRA-CSLW | PRA-CSE
The power consumption of the PRA-CSLD and PRA-CSLW is the same. Again, the power
consumption consists of a fixed part with an increment per active Ethernet port. Power is
supplied via PoE to one or both ports. Power is taken from the port that has the highest PoE
voltage. This means that if a call station is powered from two different PoE sources, like two
different PRA-MPS3 power supplies for additional redundancy, because of tolerances all of the
power may be taken from one of the power supplies. Only upon disconnection of that
Ethernet cable, the call station will take power from the other power supply. Even if both PoE
voltages are the same, using one short cable and one long cable may result in that most of the
power is taken via the shortest cable because then the voltage drop across the wire resistance
of each cable is equal.
Connecting PRA-CSE extensions to the call station will increase its power consumption
slightly, the increment depends on the number of LEDs that are on, but on average that
contribution is very limited because selections are only active during calls.
When a call station is configured for emergency purposes it may happen that a fault or failure
occurs and the buzzer of the call station is activated as an audible fault alarm. This is only the
case for emergency call stations, but the power consumption of the buzzer must then be taken
into account because the fault may not be acknowledged and then the buzzer continues.
PRA-AD604 | PRA-AD608
The PRA-AD604 and PRA-AD608 amplifiers are designed for low power consumption,
especially when powered from a battery, by incorporating different modes of operation. When
the amplifier is running on mains power and there is no audio signal present, it is operating in
idle mode on a reduced power supply voltage to keep the idle power consumption relatively
low. When an audio signal is present for one or more of the audio channels, then the power
supply voltage increases to the normal operating voltage to be able to drive loudspeaker lines
up to 100
VRMS. This increases the idle losses in the amplifier channels. Of course, when the
amplifier provides full output power to the loudspeakers, the power consumption increases
significantly. Full output power means a continuous output power of 150
W into a 600 W
loudspeaker load. Because typical speech and music signals have a crest factor of more than
9
dB, the RMS power remains below 150 W while the burst output power is 600 W.
When the mains voltage on the PRA-MPS3 fails, it switches to the battery to take power from.
The PRA-MPS3 notifies the amplifier of this and when the amplifier doesn’t have to make
announcements of high enough priority, it will go into sleep mode or snooze mode and notifies
the PRA-MPS3 to switch off the 48
VDC power section to this amplifier. The amplifier then
operates directly from the battery via the lifeline interconnection. In sleep mode the power
consumption is lowest but there is no amplifier and loudspeaker line supervision active. When
supervision has been enabled for this amplifier, the amplifier will go into snooze mode, which
is a combination of being in sleep mode for most of the time, but waking up into idle mode to
perform a supervision cycle for a few seconds every 90 seconds. The average power
consumption in snooze mode is somewhat larger than in sleep mode. When a call is being
made or a tone played to one or more of the channels, the amplifier immediately requests the
PRA-MPS3 to switch on the 48
VDC power supply again and the amplifier will operate from the
normal supply voltage. The power consumption of the active amplifier will then vary between
the value for low power (small signal audio or small loudspeaker load) and full power (audio in
full load at maximum level).
In all modes, the power consumption of the active Ethernet ports must be taken into account.
Because the PRA-AD608 has nine amplifier channels, while the PRA-AD604 has five channels,
the power consumption of the PRA-AD608 is slightly higher than of the PRA-AD604.