XPost: sci.electronics.design, sci.electronics.equipment, sci.el   
   ctronics.repair   
   From: andysnewsreply@no_junk.comcast.net   
      
   In article <0001HW.D11FE2B10634B0ABB01029BF@news.eternal-september.org>,   
   invalid@invalid.net says...   
   >   
   > One source I found says that Canon uses light from an LED--bounced from a   
   > prism at the bottom of the cartridge after ink is depleted--to trigger the   
   > "Empty" signal. Epson apparently counts the spurts of ink and calculates the   
   > arrival of "empty".   
   >   
   > I couldn't find how HP do this. Anybody know?   
      
   I believe HP just estimates based on the cartridge type it detects, and   
   the amount of ink it uses.   
      
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