What happens when you call a fax number?

If you were to call a fax number with a regular phone, a fax machine would answer and you would hear a series of beeps.

The beeps are the noise of the fax machine sending a signal to say “there is a fax machine here.” If no fax machine on your end of the phone line beeps back at the fax machine, the receiving fax machine will simply hang up the line.

https://www.youtube.com/watch?v=blra6uhnTHE