Wow, thank you. Exactly the answer I wanted.   
      
      
   *+- NEMA receptacles (1-15P) for polarized plugs have been around since the   
   late 1920s when the concept of 120/240 AC systems was fully described. We have   
   them in some old wiring in our house. NP (1-15) receptacles exist for   
   situations where the polarity    
   of the receptacle cannot be predicted - such as DC circuits, and 'back-panel'   
   receptacles in devices such are clock-radios that might be plugged into the   
   wall either way. Many more contemporary audio devices used NP receptacles in   
   the back (especially    
   tube stuff)  rather than polarized as they sometimes hummed less if plugged in   
   one way rather than another.   
      
   *+-Polarized *receptacles* offer 'safety advantages' only if they are   
   correctly wired.   
   *+-Polarized *plugs* offer safety advantages again, only if they are properly   
   wired and the device is functioning properly.   
      
   *+-These distinctions are lost on our Non-North American friends. After all,   
   it was all pretty much invented here, and the rest of the world benefitted by   
   not having to make the same mistakes we did in the beginning. Nor are they   
   living with 110 year-old    
   wiring as we are (1913). It is perfectly fine, by the way, and called "knob   
   and tube". It has also been inspected by our insurance company and passed   
   without a peep.   
      
   *+-Peter Wieck   
   *+-Melrose Park, PA   
      
   --   
   	 Vasos Panagiotopoulos  panix.com/~vjp2/vasos.htm   
     ---{Nothing herein constitutes advice.  Everything fully disclaimed.}---   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)