Question about AR/AF Timer

[chef]

Hello, I am Chef. My question about the AR timer is: How does the radio connect to the timer to make the siren go off?

http://www.jmarcoz.com/sirens/sc12.pdf

In that page above it shows how the radio wavelengths work, and it connects to the AR/F timer, but how does it activate the siren if the button is not pushed?

Thanks