touch-tone telephone voice user interfaces ( VUI/IVR )

vinodquilon said:

I am doing a tele-switch project.
I want to increase its functionality by incorporating one touch-tone VUI circuit.
My aim is to inform the caller that---
'phone is in device-mode, enter your PIN number to log in '

Can anybody help me by presenting any circuits or ICs that can manipulate my requirement ?

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