Is there any software which can act as a telephone set?

Question

is it possible to use a PC to make a phone call through your existing phone line?

Answer 1

Yes.

All you need is a Voice Modem in your PC and some telephone management software installed.

NCH makes such software:

http://www.nch.com.au/phone/index.html

NCH also provides a free softphone, called Express Talk, for making VoIP calls over the Internet using a PC.

http://www.nch.com.au/talk/index.html