Raymarine Limited. Registered in England. Company no. 1177969
Page 20
Registered Office: Anchorage Park, Portsmouth P03 5TD
In the OPERATE mode the amplifier is operating normally. The operating mode is activated when
the mode pin is less than 0.5 V.
The gain of the amplifier is fixed at 32dB. An input attenuator (including the volume control) ensures
that the input presented to the amplifier will produce a rated power output of 5W at the speaker for
830mV rms 1kHz sine wave at the input to the active speaker.
MUTE
The mute signal is floating for normal operation, and low when the unit is muted. If the volume
control switch is not in the OFF position, i.e., such that the integral switch in the volume control is
closed, then the mode pin on the amplifier is held at mid-supply rail by a couple of 10k resistors. The
output of the amplifier is the MUTED. The mute operation is overridden by the volume control
switch, such that the system can be placed into STANDBY mode when the switch is in its off
position, irrespective of the level on the mute pin. In standby mode there is no output from the
amplifier. The mute mode is also overridden by the ALARM mode.
Alarm Override
An alarm override control is fitted to the amplifier such that it is possible to override the mute and
volume control settings to output a DSC alarm condition. When the Alarm mode is activated the
amplifier will output an alarm mode in excess of 80dB spl at 1m. Operation of the alarm can only be
cancelled from the RAY240 handset. Turning the volume control knob will have no effect in alarm
mode. The alarm mode signal is carried on the same wire as the microphone signal from the RAY240
handset. The microphone signal will never achieve a signal level greater than 3.3V, since the signal is
supplied from a single ended op-amp running from a 3.3V supply. This is not a sufficient voltage to
trigger the alarm mode in the speaker. Alarm mode is activated in the RAY240 main processor box
by pulling the signal line high t0 12V. When the signal exceeds approximately 6V, the alarm mode in
the amplifier is entered.
