tone dialling 
noun [mass noun]
A method of telephone dialling in which each digit is represented by a particular combination of tones.To set it up correctly for tone dialling you have to remove the front cover on the control panel....
- If you can use tone dialling, the amount of time it takes to dial can be changed using the S11 register.
- It is possible to include both pulse and tone dialling within the same dial string.