Dual Tone Multi Frequency (DTMF) - Signal Identification Wiki
Nerd Club: Telephone dialler (DTMF tone generator using PIC 16F1825) for dementia sufferers
ToneDef (DTMF Tone Dialer) - Apps on Google Play
For Pulse to tone multi frequency DTMF converter enhanced version of old dial telephone / pulse to double tone module|pulse to tone|pulse to tone converterpulse to dtmf - AliExpress
Nerd Club: Telephone dialler (DTMF tone generator using PIC 16F1825) for dementia sufferers
DTMF TONE DIALER
File:DTMF Dialer Inside.jpg - Wikimedia Commons
DTMF, Dual Tone Multi Frequency, MT8870DE DTMF Decoder