TCC Telephone Analyser
Some resource:-
https://www.microchip.com/wwwAppNotes/AppNotes.aspx?appnote=en591264 - Generate DTMF using PWM - atmel https://lh3.googleusercontent.com/-oa5T-7XZ2I0/UeIkeFvSdsI/AAAAAAAAAcU/ZICBACaH2zw/w1277-h378-no/Schematic_v1-0.png - rotary phone interface https://www.dmcinfo.com/latest-thinking/blog/id/8627/updating-your-rotary-dial-phone-for-the-digital-age - rotary phone interface for DTMF generation https://code.google.com/archive/p/miscellaneous-projects/source/default/source https://hackaday.io/project/28557-pulse-to-tone-converter https://www.elenco.com/wp-content/uploads/2017/10/AK-700_REV-P_062608-2.pdf https://www.digchip.com/datasheets/parts/datasheet/433/SC91415CK.php https://www.tutorialspoint.com/telecommunication_switching_systems_and_networks/telecommunication_switching_systems_and_networks_touchtone_dial_telephone.htm https://downloads.avaya.com/elmodocs2/ir/28096.htm#:~:text=Dial%20pulse%20input%20can%20be,T1%20or%20E1%20digital%20interfaces.
http://www.picbasic.co.uk/forum/showthread.php?t=21104 - imp