Tone burst generator
Electronic
74HC00

A tone generator is an oscillator that sends out signals repeated at regular intervals, as shown in Figure 1.

As its name suggests, a speaker is usually used to let you hear the tone it makes. But in this project, we're going to use an LED to find out how it works.

You can see from the schematic, IC U2 is a tone generator whose frequency can be changed by 100K control volume.

IC U1 is another generator which controls the start and stop of the tone generator. Its frequency can also be changed by turning 50K control volume, and its duty ratio can be adjusted using S1 and S2. Remember what the duty ratio is?

The duty ratio is about 24% when S1 is ON, and about 76% when S2 is ON. This project can be used as a logic circuit whose waveform ends in an integer cycle.

When you finish assembling the project, turn power ON and see what the LED is doing. Does it blink ON and OFF as shown in Figure 1?

Then, turn 50K control volume and press S1 and S2, and see how the LED changes its blinking intervals.