Abstract: An apparatus and method are provided for detecting radio accessories within a communication system formed of a radio, a primary accessory and a secondary accessory. The secondary accessory comprises a resistor network which switchably couples parallel resistors in response to a bias input generated from either a microphone bias voltage or speaker bias voltage of the primary accessory. Various parallel combinations of the resistors indicate the secondary accessory type. Control logic in the primary accessory determines the type of secondary accessory by comparing digital signals representative of the current sourced through the resistor network (175) to predetermined values stored in look-up table. The utilization of the microphone bias and/or speaker bias of the primary accessory advantageously negates the need for any additional pins or complex circuitry at the primary accessory.

Abstract: An apparatus and method are provided for detecting radio accessories within a communication system formed of a radio, a primary accessory and a secondary accessory. The secondary accessory comprises a resistor network which switchably couples parallel resistors in response to a bias input generated from either a microphone bias voltage or speaker bias voltage of the primary accessory. Various parallel combinations of the resistors indicate the secondary accessory type. Control logic in the primary accessory determines the type of secondary accessory by comparing digital signals representative of the current sourced through the resistor network (175) to predetermined values stored in look-up table. The utilization of the microphone bias and/or speaker bias of the primary accessory advantageously negates the need for any additional pins or complex circuitry at the primary accessory.