i need to monitor signals from(on) a PSTN(POTS) line.
These signals are as follows
(1) when the telephone is/has (been) answered
(2) when the telephone is/has (been) answered by a
human
(3) when the telephone is/has (been) answered by an
answering machine
(4) when the telephone is/has not (been) answered
(5) when the telephone you are calling is busy

can some one give some ideas?