Toner Cartridge Detection The Toner Cartridge has a Toner sensor. The circuit compares the output value of the developing AC bias and the output value from the antenna inside the Cartridge, and outputs the Toner detection signal. The CPU detects the remaining Toner level and the presence of the Cartridge when the developing bias is applied to the Developing Cylinder. The remaining Toner level is always detected when the developing bias is applied. The presence of the Cartridge is detected only when the developing bias is applied during the initial rotation. Power Supply System 5-5