Is there any way to use my iMac to ring my mother's landline?

I certainly cannot see any simple and obvious one.

She has a computer and I can get her on FaceTime or Skype sometimes but she has a habit of leaving the computer closed (its a laptop) because her cat keeps walking over it!

I'd like to call her home phone from my computer (we have no landline) on our VDSL connection but there seems to be no immediately apparent way to do so.