From the Manufacturer
With the Plantronics PC Headset Speaker Switch you can now can use your computer speakers and headset at the same time. No more fumbling around with plugs and wires when you want to use your headset instead of your speakers. The Plantronics PC Headset Speaker switch allows you to easily swap between the two at the touch of a button. Its small size takes up very little space. This switch is a convenient solution to your headset needs that takes only seconds to install. Just plug it into the sound card and you're ready to go. Compatible with any PC or Macintosh computer that has a sound card.
Now you can use your computer speakers and headset at the same time with this Plantronics PC Speaker Headset switch. You can easily swap between your speakers and headset at the touch of a button. Its small size doesnM-^Rt take up any space and it installs in seconds. Plus, it mutes the microphone in the speaker position.