A:Answer the photo of the back panel shows an "AC IN" switchable power outlet for the purpose of controlling a plugged in, external device that uses household current, such as a power amp (e.g. for a powered external subwoofer) using your Pioneer receiver's on/off (remote controlled) front switch of the receiver. so when you power on the receiver, that external power amp etc. that is plugged into the back will power on simultaneously with the home theater system controlled by the receiver. this is a safe and convenient way to turn on any electrical devices plugged into the back AC outlet, so you do not have to switch them on separately. So, as with my legacy Pioneer A/V receiver, the purpose of this Pioneer's rear AC outlet is NOT to plug foreign country electrical devices using 50Hz/220V into your receiver!!! not a good idea in any situation!!! Pioneer is the only brand that offers this very convenient feature for turning on all high voltage devices in the HT audio system on and off simultaneously, which is also nice if you don't want to forget to turn something off that will run all day and rack up your power utility bill (like high powered subwoofer amps etc.) because you forgot to turn it off.
