CROSS PERSONAL: Service & maintenance manual - rev. 1.1
Page 3.14
The CPU card sends a 12 Vdc signal to the amplifier to power it as well as the audio signal.
To avoid creating disturbances for the end user, by reproducing the audio signal from more than
one channel, the system permits the signal to be listened to from only one of the 3 channels, with
the following order of priority: Headphone jack socket, audio output jack socket, speakers.
In particular, when headphones are connected to the jack socket on the frame immediately under the
display, the signal to the output jack socket at the base of the frame is “mechanically” cut off and a
signal is sent to switch off the amplifier so that no sound is put out by the speakers (POWER OFF
signal interrupted).
In the same way, if an external system is connected to the jack socket at the base of the frame, a
signal is sent to switch off the amplifier so that no sound is put out by the speakers (POWER OFF
signal interrupted).
If no device is connected to the 2 jack sockets, the audio will be played through the equipments
speakers, and the signal will be further amplified than the one sent out by the CPU.
3.4.2. THE SIGNALS INVOLVED
The following signals are involved in the control:
• Power signal
This is a 12Vdc signal that the CPU card sends to the amplifier to power it.
• Audio signal
This is the signal that includes the two R-L audio channels, sent by the CPU to the amplifier and
then to the audio output jack socket or to the speakers.
• Amplifier Power OFF signal
This is the signal sent by the two jack sockets to the amplifier, to switch it off, thus avoiding
audio reproduction by the equipment's speakers.
It is not an actual separate signal, but uses one of the audio channels output by the jack socket
which, when cut off due to connection of a jack into the jack socket, is interpreted by the
amplifier as a switch-off signal.
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