The noise you hear when you pick up a telephone to tell you it is working and waiting for you to dial a number.
Normally you dial * then 6 then 7. If you are using a rotary phone, you can dial 1167 instead of *67.
It is a dial tone ( like Morse Code) and functions as the carrier wave for the phone call, once ( dialed up) the message traffic rides on the carrier. ( not necessarily Flat on top- pun intended with...
you my face that problem because of network or have access to internet.
ring ring xx