Toner cartridge identifying apparatus for an image forming apparatus

An image forming apparatus includes a replaceable toner cartridge which, in turn, includes a magnetic chip which records identifying information about the type of toner cartridge. The magnetic chip interacts with an identifying unit, to determine the compatibility of the toner cartridge. The magnetic chip is made from magnetic powder and non-magnetic powder compounded at an appropriate ratio at which a predetermined magnetic resistance is maintained. The identifying unit includes a magnetic sensor which detects magnetic resistance without contacting the magnetic chip. A microcomputer verifies whether the output detected by the magnetic sensor is greater than or equal to a predetermined level and within a range of criterion, to determine whether the toner cartridge is compatible with the image forming apparatus.