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I disagree with the Wikipedia statement that an amplifier with feedback makes it bilateral.
Consider an opamp with negative feedback. The input to this amplifier is a resistor to a summing point, the negative input of the chip, to this same summing point is a resistor from the amplifier output. Theoretically the voltage at the summing point is zero. Therefore, the signal input to the input summing resistor is totally unaffected by any change applied to the output of the amplifier.
If you apply a signal to the output of the amplifier it will not change the output and does not have any effect at the input.
Essentially this opamp circuit is a voltage source with zero output impedance and therefore a signal of finite internal impedance can not change the output of the opamp circuit. In the real world within the normal operating range of this circuit the output impedance is very small.
If an external change at the output of a circuit can not make a change at the input, then it is not bilateral.
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