Oh yes, other things you need to do

Detect the voltage drop on the phone line. I think it goes
from ~48VDC to ~8VDC when the handset is picked up.

Your circuit might also be able to withstand the ring voltage,
and I believe this is ~100V (???), but that could depend on
the switching arrangement you choose

Detect a dial tone (400Hz ?). Either with the PIC or an LM567

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