| 摘要 |
PURPOSE:To facilitate level adjustment by adjusting the gain of an amplifier which connects a photosensor and an A/D converter so that the input level of the A/D converter exists between a maximum and a minimum permissible level when a medium for adjustment is inserted into a detection part. CONSTITUTION:When the medium 1 is inserted into the detection part 2, light from a lamp L does not reach the photosensor 3, so detection is performed. Detection currents A and B when the medium is inserted and not inserted are amplified by an amplifier 4 while A>B and inputted to an A/D converter 5, where they are converted into digital signals D. The signals D are compared with the maximum and minimum permissible levels of registers 9a and 9b by comparators 7a and 7b and a display device 8 is turned on by an AND gate 10 only when the signal is between both levels. Therefore, a variable volume control Rv so that the display device 8 turns on or off on optimum condition. |
