A power of 2 is chosen so a simple chain of digital divide-by-2 stages can derive the 1 Hz signal needed to drive the watch's second hand.

Interestingly the experiment also demonstrates a leftover 17 Hz signal, but the authors assume it is linked to the laboratory.

When the signal is received in the aircraft, the two 30 Hz signals are detected and then compared to determine the phase angle between them.

That means the dots and dashes have become pulses of a 45000 Hz signal, which is inaudible.

The system had two 60 Hz signals.

The original Indusi system was deployed since 1934 which however had only a train stop function (the 2000 Hz signal in later revisions).

A 2400 Hz signal with a length of five seconds marks the beginning of a transmission and is used for synchronization of the reading program.

At the end of the transmission, a 2400 Hz signal with a length of one second is sent.

The 60,000 Hz signal is always transmitted, but every second it is significantly reduced in power for a period of 0.2, 0.5 or 0.8 seconds:

A camera with a Sync motor sends a 60/50 Hz signal to the recorder, which is recorded as a sine wave pilot tone.