My prototype interfacing At89c2051 with
MT8880 to dial a number.
The signal number dialed just fine on
oscilloscope, but whenever connected to
the telephone line, the signal is disappeared.

I have tried by coupling the signals trough
a 600 ohm 1:1 transformer to the line.

Also by coupling the output of the 8880 through
a resistor of 100k and a capacitor of 0.1 uF.

Any one out there please,
I need help.

Thank you in advance.