What are the tones called when you press a key on your telephone?

What are the tones called when you press a key on your telephone?

• Multiple Frequency Tone Signal
• Dual Signal Tone Frequency
• Dual Tone Multiple Frequency (MF4)
• Single Tone Frequency 

EXPLANATION

DTMF (dual tone multi-frequency) is the beeping signal to the phone company that you generate when you press an ordinary telephone's touch keys.

https://en.wikipedia.org/wiki/Dual-tone_multi-frequency_signaling

SOURCE