Building An Alarm Phone

[Sobakava]

I need to make a device similar to usual phone,

it should dial recorded number when "call" button pressed,
after remote side picks-up the handset, it should provide
handsfree talking... that's all...

I plan to use a very simple microcontroller for dialing number
using dtmf.

but I need recommendations about line interfacing of microphone,
speaker phone and dtmf signal produced by the microcontroller.

regards

 

[armsgroup]

try this

https://www.electronic-circuits-diagrams.com/telephones_circuits.shtml

 

[xirix]

Watch RAT ring on yahoo: you'll find a easy to build interface.