| 摘要 |
PURPOSE:To detect seucrely that the ink level is under a given value by a method wherein shortage of ink is detected by the output of an ink-level-detecting-means in an ink tank and the output given at a definite time after the said output. CONSTITUTION:If a switch S is turned off when a given time, for example, 30 seconds pass, the output A of an inverter IN1 does not hold a high level, no output is obtained from AND gate AND and shortage of ink is not detected. Then, when the switch S shuts again, the output A of the inverter IN1 takes a high level and a signal shown by (c) is given, at the rise of this output A, the terminal of the monostable multivibrator M takes a high level and a terminal Q' takes a low level for thrity seconds. Thrity seconds after, when the terminal Q' returns to a high level, the output A of inverter IN2 holds a high level, the output B of the AND gate AND takes a high level, a light emitting diode LED is lighted and shortage of ink can be indicated. |
