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Shutdown Mute
Figure 40
The Audio Amplifier will be placed in a Standby mode and the set will shut down if a DC voltage is
detected on the Speaker Output lines. The Left and Right audio output lines are connected to the
base of 7704 and the emitter of 7705 via resistors 3718 and 3717. Filter capacitor 2778 filters out the
AC component of the waveform. If the DC voltage goes positive, 7704 will turn On. If the voltage goes
negative, 7705 will turn On. This turns 7706 On. It also turns SCR 6701 On, turning transistor 7708
On, causing the Standby line to go High. If this SCR is turned On, it will be necessary to remove
power from the set to reset the circuit. This will turn the set Off. Transistor 7707 also turns On,
causing the Standby-Mute line to go Low. This places the Audio Output IC in a Standby mode. If the
Power Fail line should go High, 7710 will turn On, causing the Standby-Mute line to go Low.
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