The goal of this circuit is to have the speaker produce a siren sound, however, I don't understand how the second 555 accomplishes this.
I understand that the output of the first 555 will be fed into the Resistor/Capacitor pair. When the pulse goes HIGH, the capacitor will be charged and once the timer flips, the capacitor will be discharged, which will cause the pulses to look like this.
This output is then fed into pin 5 on the second 555. This is the part that I don't understand. What exactly does the second 555 do, that makes the speaker produce a siren sound?
Thank you in advance.