US Patent 7272328 Development component detection in an electrophotographic device

An image forming device and method of detecting the presence or absence of components of one or more image forming units. Each image forming unit includes a replaceable component. A power supply transmits an input signal to the replaceable component. A detection circuit is coupled to the replaceable component and generates an output signal indicative of the presence or absence of an electrical coupling that is established when the replaceable component is installed. The detection circuit thus senses the input signal propagating through the replaceable component. A controller may be adapted to halt image formation or generate an error indication if the detection circuit detects the absence of necessary components or the presence of components not necessary for a current mode of operation.