The printer detector chiefly possess : Low paper detection utensil ( PE's detector ), paper bail place detector and sending the paper accent staff place detector. These three kinds of detectors' examination elements shall transform the signal needing to be fathomed into voltage signal and then output, and utilizes convertor and signal transfer to succeed the signal conversion transmitting voltage that has the drive capability with treatment of signal and so on again. The printer detector plays the significant action in the regular work of printer.