To take full advantage of this feature, your TV must support a standard called HDMI-CEC. Not all TVs support this, so unfortunately there may be cases where this feature doesn't work.
To set this up:
Go to the Spark tab from the bottom navigation
Click on "Setup HDMI Ports"
In the first select menu, select HDMI Port 1 - 4 that indicates where the Spark is plugged in.
In the second select menu, select a different port that indicates the port that you watch TV on and switch to when a call is complete. Note: if you're using Antenna or a TV Tuner, the Spark will not be able to switch to that at this time.
Now, if you want to make a call, your Spark will switch to itself when the call starts, and switch back to your TV port when the call ends. Magic!