Ringtone on computer not headset when calling someone

Hi.  I have my computer set up with the speakers as the default audio device and the headset to be used during calls. However, when I ring someone it plays the ring on the speakers of my computer rather than through my headset. I'm pretty sure this is rather annoying for others in our office! How can I make it so that when calling someone the ring plays in my headset but when I am called by someone that still rings on the speakers?

Thanks.