Telephone MF Tones


This is only of historical interest but de rigueur for a website.

700900110013001500
9001
110023
1300456
15007890
1700ST3ST2KPKP2ST

And of course there is the tandem frequency of 2600 Hz.

1209133614771633
697123A
770456B
852789C
941*0#D

Note that there is a step of exp(0.1) between each frequency and a step of exp(0.25) between the lower and upper bank.