BC147 Balance display circuit

This Balance display circuit,be the circuit shows the equilibrium in the sound in stereo system. By indicate that stereo system signal on the left and right have or not is a signal equal ? Which if signal both of channel left sound and right channel equilibrium or balance prevent. The LED bilateral switch off but conversely if 2 both of channel sounds are rough LED any one stick bright.
When one party power circuit. And input audio stereo signal into the input box if the left and right channel audio signal equal to the Q1 and Q3 the same stream. There was no difference in the LED voltage on both be ill. If the signal is not balanced. Hypothetical signaling through the right channel signal rather than left to the LED1 and LED2 light off signal indicating that the signal over the right-left channel.