The ADF-700 AM receiver is a solid state digital airborne automatic direction finder receiver that determines relative bearing to any selected transmitter operating between 190 kHz and 1750 kHz. When a frequency is selected in the cockpit by a control it converts the frequency selected to ARINC 429 code to transmit through the aircraft data bus to the ADF-700 to cause it to tune to the frequency selected. Bearing information of the received signal is then sent to the bearing indicator for display while aural intelligence is presented to the aircraft intercom system. The ADF-700 receives RF signals from three antennas and determines the relative bearing between the center line of the aircraft and the selected station. The signals received may include any in the normal broadcast band from commercial broadcast ground transmitters. Ground transmitters are located at known coordinates around the world which transmit AM modulated station identification codes, weather and flight information. This information is converted into ARINC 429 format for transmission to the aircraft-bearing indicator.

 The ADF-700 consists of sub-assemblies and a chassis assembly housed in a 2-MCU-size case. The equipment consists of an aluminum chassis to provide mounting and Collins surfaces for the major sub-assemblies. Cooling air is circulated freely throughout the unit through holes provided on the top and bottom of the chassis. Three self-test indicators and a self-test button are located on the front panel with a foldaway handle that facilitates removal from the rack and carrying the ADF-700. A hold-down is supplied on the front to secure the LRU to the aircraft equipment rack. Electrical connections are made through an ARINC 600 connector on the rear of the chassis. The ADF-700 is directly interchangeable with installations that have full ARINC 712 wiring. The ADF-700 works in association with an indicator which displays aircraft magnetic heading, course and relative bearing between aircraft heading and the direction of the selected signal source. The ADF-700 also requires a sense (omnidirectional) antenna that is vertically polarized in the horizontal plane and 2 loop (directional) antennas that are orthogonally-polarized with one antenna being longitudinal and one being lateral. The ADF antennas must be able to receive signals in the 190 kHz to 1750 kHz range.