en | Supervision
Supervision is provided for:
Relays are provided on the rear panel for the each supervised function and are normally
energized (fail‑safe). Each relay has 3 contacts, normally open, common and normally closed.
If an application does not need supervision, the indicators on the front panel can be set to
"OFF" with the switches next to each relay output. The relays always function and are
independent of the indicator switch setting.
Input pilot tone
The Plena Voice Alarm System uses a pilot tone of 20kHz at -20dBV to supervise the pre-
amplifier, the connections between the pre‑amplifier and the power amplifier and function of
the power amplifier. If the input signal from the pre‑amplifier stops, the mains and battery fail,
or the power amplifier stops for any other reason, the pilot‑tone stops, the pilot‑tone fault
indication shows on the front panel and a signal is given on the Input fault relay. If the power
amplifier stops through overheat, then the overheat indicator shows on the front panel, the
signal is given on the Input fault relay.
The pilot‑tone detection indicator can be set to "ON" or "OFF" with the pilot‑tone detection
switch (17), see Rear panel connectors and switches, page 9. The pilot‑tone indicator on the
front panel is set to "OFF", but the fault relay switch still functions.
The power amplifier supervises the availability of the back‑up power supply.
If the battery supply fails the battery fault indication shows on the front panel and the battery
fault relay switches over.
The battery supervision indicator can be set to "ON" or "OFF" with the battery detection
switch (15), Rear panel connectors and switches, page 9. The battery indicator on the front
panel is set to "OFF", but the fault relay switch still functions.
The amplifier will work between 20VDC and 26.5VDC. Below 20VDC the amplifier will shut
down if the mains is not present.
The amplifier will automatically switch from primary power (mains) to backup power (24VDC),
this changeover is automatic. During switch over a glitch can be heard in the audio signal,
typically this lasts less than 1 second, maximum 2 seconds duration.
The power amplifier supervises the availability of the mains supply. If the mains supply fails
(falls below the threshold of -20%), and the back‑up power supply takes over, the fault relay
moves to the NOK position. A mains fault indication shows on the front panel and a fault state
is given by the mains fault relay.
2014.01 | V1.1 | LBB193x/x0
Pre‑amplifier and power amplifier function
Battery and mains supervision
Installation and Operation manual
Plena Power Amplifiers
Bosch Security Systems B.V.