| 摘要 |
PURPOSE:To improve the reliability of a circuit and to increase the cost of the device by deciding the mounting of a developing unit on a main body device and whether toner is present or not from the signal inputted to an input terminal. CONSTITUTION:When the toner becomes deficient, a piezoelectric element 17a begins to oscillate gradually, its oscillation becomes continuous oscillation is order, and the oscillation signal of the piezoelectric element 17a is inputted to a CPU 22 through an input terminal 21-2. The CPU 22 displays a no-toner display on a display part and the deficiency of the toner in a developer container is securely detected. When the developing unit 12 is not mounted, in earth line l3 is not connected, so a voltage having the earth level completely is inputted to the INT terminal of the CPU 22 by a pull-down resistance RD and the CPU 22 judges that the developing unit 12 is not mounted and resets a flag. Consequently, the percent defect of the circuit decreases and the reliability of the device is improved. |
