How can we detect an in-comming phone call using PC's modem .
How can we detect an in-comming phone call using PC's modem .
I am not sure I understand. This is normally the job of the modem. You can set this using the AT command set for your particular modem.
Using a terminal emulation program you can use the command ATA to answer the phone manually - or you can set the modem to auto answer, but you will have to check your documentation for this. There are a couple of different AT command sets that allow you to customise the way it answers the phone.
Do a search on google for "hayes AT commands".
I may have totally misunderstood what you are asking, but your question was a little cryptic.