This is not simply a voltage level signal. It is a precise communication protocol where the receiving device — a servo, ESC, or flight controller — measures the exact duration of each incoming pulse in microseconds and acts on that value.

The signal runs at a fixed frequency of roughly 50 Hz, meaning one pulse arrives every 20 milliseconds. The magic is in how long that pulse stays high:

The servo or ESC contains a dedicated timer circuit that measures these pulse widths and responds accordingly. A 1500µs pulse at 50 Hz represents roughly a 7.5% duty cycle — but that number is meaningless to the servo. Only the 1500µs matters.

This type of PWM is simply using rapid on/off switching to approximate an analog DC voltage. There is no protocol, no timing decoder, and no microcontroller on the receiving end measuring pulse widths.

The output switches between 0V and the supply voltage (e.g., 3.3V or 5V) at a high frequency. Either an RC filter or the natural capacitance/inductance of the load smooths this switching into a stable DC level. The relationship is simple:

Frequency matters only insofar as it needs to be fast enough for the RC filter to smooth out the ripple. There's no requirement for it to be 50 Hz, and the absolute pulse width in microseconds is irrelevant.