This information is then fed over an analog or digital interface to one of four common types of indicators:
A typical light-airplane VOR indicator, sometimes called an "omni-bearing indicator" or OBI[7] is shown in the illustration at the top of this entry. It consists of a knob to rotate an "Omni Bearing Selector" (OBS), the OBS scale around the outside of the instrument, and a vertical course deviation indicator or (CDI) pointer. The OBS is used to set the desired course, and the CDI is centered when the aircraft is on the selected course, or gives left/right steering commands to return to the course. An "ambiguity" (TO-FROM) indicator shows whether following the selected course would take the aircraft to, or away from the station. The indicator may also include a glideslope pointer for use when receiving full ILS signals.
A Horizontal Situation Indicator (HSI) is considerably more expensive and complex than a standard VOR indicator, but combines heading information with the navigation display in a much more user-friendly format, approximating a simplified moving map.
A Radio Magnetic Indicator (RMI), developed previous to the HSI, features a course arrow superimposed on a rotating card which shows the aircraft's current heading at the top of the dial. The "tail" of the course arrow points at the current radial from the station, and the "head" of the arrow points at the reciprocal (180° different) course to the station. An RMI may present information from more than one VOR or ADF receiver simultaneously.
An Area Navigation (RNAV) system is an onboard computer, with display, and may include an up-to-date navigation database. At least one VOR/DME station is required, for the computer to plot aircraft position on a moving map, or display course deviation and distance relative to a waypoint (virtual VOR station). RNAV type systems have also been made the use two VORs or two DMEs to define a waypoint; these are typically referred to by other names such as "distance computing equipment" for the dual-VOR type or "DME-DME" for the type using more than one DME signal.