Look on the westinghouse remote, at the top you have a series of buttons that say TV, DVD, VIDEO, HDMI, etc.
You'll need to press one of those, depending on where the cable box is connected, to get back to the proper input.
If your cable box is connected with a coax (round screw on cable) you need to be on TV mode and the TV set to channel 3 or 4.
If the comcast box is connected with hdmi, press hdmi, or if red/white/yellow press video, and so on.
Once you get back to the proper input, then you can use the comcast remote to change channels from there.
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