Step  - Watch The Tv; Step 3 - Listen To The Sound - Logitech Harmony One User Manual

Step  — Watch the TV
In this step, you must use your TV's original remote control to switch between inputs.
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3.
Step 3 — Listen to the sound
You need to complete this step only if you have a separate device (called an AV
Receiver) that manages the sound for your entertainment system. For example, you
have a home theater system or connect your TV to your stereo so the sound comes out
of your stereo speakers.
You must use your AV Receiver's original remote control to switch between inputs.
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.
3.
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Using your TV's original remote, select each input one-at-a-time.
For each input, note which device appears to be connected to that input.
For example, if you switch to VIDEO 1 and see your DVD playing, you know
your DVD player is connected to VIDEO 1.
Repeat step  for each input.
Using your AV Receiver's original remote, select each input one-at-a-time.
For each input, note which device appears to be connected to that input.
For example, if you switch to OPTICAL 1 and hear the sound from your DVD
playing, you know your DVD player is connected to OPTICAL 1.
Repeat step  for each input.