ZBM2

https://hackaday.com/2015/03/09/convert-a-rotary-phone-to-voip-using-raspberry-pi/

https://stackoverflow.com/questions/29637142/raspberrypi-making-sip-outbound-calls-using-linphonec-or-an-alternative-sip-sof https://www.voip-info.org/asterisk-phone-linphone/

https://github.com/pjsip/pjproject

https://hardfault.life/p/telco-1 https://hardfault.life/p/telco-2

Turn handle to connect with voice controlled switchboard - Which extension do you require? emulate correct phone tones?

Rotary, Handle, button push