The two signals $$S1$$ and $$S2,$$ shown in figure, are applied to $$Y$$ and $$X$$ deflection plates of an oscilloscope.

The waveform displayed on the screen is

In an oscilloscope screen, linear sweep is applied at the

A dual trace oscilloscope is set to operate in the ALTernate. The control input of the multiplexer used in the y-circuit is fed with a signal having a frequency equal to

The two inputs of a $$CRO$$ are fed with two stationary periodic signals. In the $$X$$-$$Y$$ mode, the screen shows a figure which changes from ellipse to circle and back to ellipse with its major axis changing orientation slowly and repeatedly. The following inference can be made from this.