Abstract: An apparatus for identifying the identity of an accessory device connected to an electronic device using a voltage divider circuit, an analog to digital converter, and a database associating various digital values with the identity of various accessory devices. The voltage divider circuit includes a first resistor located within the electronic device and having a single resistance value. The voltage divider circuit also includes a second resistor located within the accessory device whose resistance value varies between accessories such that a distinct voltage value is applied to the analog to digital converter for each accessory. The digital output value of the analog to digital converter is compared with a list of values stored within the database to determine the identity of the accessory device.

Abstract: Signal level control for an amplifier or the like is provided by a binary counter which counts upward when first operated, and which thereafter counts up and down if continually operated. If the operated counter is stopped after counting up, it counts up when operated again. If the operated counter is stopped after counting down, it counts up when operated again. A digital to analog converter can provide a single control signal from the counter. The user is always assured that the single control signal will increase when the counter is operated again following a prior operation in either direction.

Abstract: A paging receiver selectively operable in either a six tone battery saving mode or in a five tone non-battery saving mode. The receiver features a serial code plug for programming a programmable tone detector to be responsive to a specific paging receiver address comprising a predetermined combination of preamble and paging signals. The use of a serial code plug in place of the parallel code plug previously known and utilized in the industry allows a reduced complexity of the paging receiver and a corresponding size, weight and cost savings.