Why does “PROTECT” message appear in the front panel display?

The unit needs to be connected all speakers.
When there is a speaker which is not connected to the unit, "PROTECT" message might appear in the front panel display. If "PROTECT" appears, please perform the followings:

1. Connect all channels to their corresponding "SPEAKERS" terminals correctly.
2. Press to turn off the system, and check the following items after "STANDBY" disappears:
   - Are the + and – speaker cords short-circuited?
   - Is anything blocking the ventilation holes of the system?
3. After checking the above items and fixing any problems, turn on the system. If the cause of the problem cannot be found even after checking all the above items, please consult your nearest Sony dealer.