| 摘要 |
PURPOSE:To detect a less residual amount and shortage of recording paper by only one detecting circuit only by adding a detecting signal discriminating circuit and a residual amount discriminating circuit to enter a mark of a prescribed fine line on the recording paper. CONSTITUTION:A roll recording paper 1 is held on a spool 11. Light from a light emitting diode 21 irradiates the back side of the recording paper 1 and the reflected light is received on an optical sensor 22, and an output voltage from the optical sensor 22 is amplified inversely at an inverse amplifier 23 and outputted as a detecting signal A. The signal A is supplied to a detecting signal discriminating circuit 3. The length of time of ''H'' of the signal A is compared with a preset time, and when it is longer than the preset time, a recording paper shortage signal B is outputted. When the consecutive time length of ''L'' of the signal A is longer than the preset time, a reset signal C being at ''L'' is outputted to a residual amount discriminating circuit 4. |
