English: This visualization describes phase modulation.

The wave displayed in red is the carrier signal, a sinusoidal wave with its frequency doubled base frequency. The wave displayed in blue is the modulating signal, also a sinusoidal wave, with its frequency tripled the base frequency. This modulating signal is positioned perpendicular to the carrier signal for the purpose of visualizing this type of modulation.

The modulating signal (blue) determines the instantaneous phase of the carrier signal (red) of which current value will be the resulting signal. --- To generate this visualization, we first draw the carrier [t-2π; t 2π] and modulating signal [t; t 4π] perpendicular to each other; the modulating signal x-axis is aligned with the carrier's y-axis.

We then draw a line from the modulating signal's value at time t and extend it until it intersects with the carrier signal. We then draw a line from that intersection until we intersect the reflector (45-degree backslash line) and extend it horizontally until we reach the output signal's buffer.

The equation is g(x) = π/2 * sin( 2 * 2π * t π/2 * sin( 3 * 2π * t ))