The EFD-84 is a panel mounted 4 inch CRT display. The EFD-84 displays information supplied by a DPU-84 Display Processor Unit or MPU-84 Multifunction Processor Unit. The EFD-84 can function as an EADI and EHSI, or a radar indicator. When the EFD-84 is used as an Electronic Attitude Director Indicator (EADI) it presents a multicolor CRT display of aircraft pitch and roll attitude, autopilot mode annunciations, vertical deviation, lateral deviation, autopilot engage status, attitude/heading comparator warnings and decision height set. Other displays are displayed as a function of pilot selection or operation mode such as attitude source, radio altitude, excessive ILS deviation and comparator warning, fast/slow deviation or angle-of-attack deviation and marker beacon. Interconnect strapping enables more display options such as cross pointer or command bars, speed deviation display inhibit, enable or inhibit rising runway and enable or inhibit composite format in reversion. Electrical connections to the EFD-84 are made through two 25-pin keyed Cannon D-type connectors. The connectors are physically mounted to circuit card assemblies inside the unit and extend out through the chassis and cover at the rear of the unit. Threaded screw holes are provided in the bezel assembly for mounting an inclinometer when the EFD-84 is used as an EADI. When the EFD-84 is used as EHSI a cover plate is installed on the bezel assembly over the area that would otherwise be occupied by the inclinometer.

Each EFD contains a CRT, deflection yoke, video and deflection amplifiers and high-voltage power supply. The CRT is a Collins specified custom high resolution color tube. The tube has an in-line gun with shadow mask, using a black matrix surrounding pigmented phosphor dot trios, providing high resolution and contrast ratio. A custom design multi band pass optical filter is used to enhance contrast. Both stroke and raster scanning techniques are multiplexed to provide large area color background and sharp alphanumerics and symbols with greater than normal illumination. Two units stacked use the same panel space as the EFIS-84 electromechanical units. All EFD's are identical internally.

The EFD-84 also provides a high temperature warning output that can drive an external installer-supplied annunciator .This annunciator will illuminate if the internal temperature of the EFD-84 reaches +95 °C (+203 °F) in still air.The EFD-84 requires the air behind the cockpit panel to be circulated to ensure optimal performance. These units are capable of operation for a short time at the elevated operating temperatures specified in the environmental section of this specification without cooling air. However, operation at these levels is not considered normal. The EFD-84 is enclosed in a housing which has cooling air holes on the top, bottom, both sides, and rear surfaces. The EFD-84 has an integral cooling fan mounted on the rear of the unit. The unit mounting flange is attached to the outer surface of the instrument panel.