The King Radio KDM 7000B Distance Measuring Equipment

1. What the "7000B" is

In briefThe name "Bendix/King 7000B DME" alone does not say whether it was an airborne unit or a ground beacon. The sources settle it: it is the KDM 7000B, an airborne DME interrogator built by King Radio Corporation in Olathe, Kansas, and sold under the Bendix/King name after King and Bendix were combined [1][12][15]. An Australian airworthiness directive from February 1989 names the "King KDM 7000B Distance Measuring Equipment" and its part numbers [1]. A Boeing 747 maintenance manual calls it a "KDM 7000/B DME interrogator" [4]. No ground DME called "7000" or "7000B" was found. The author's own training certificate from January 1993 names the family "KDM 7000/A/B Digital DME" [29].

DME, short for distance measuring equipment, is one of the oldest radio navigation aids still in daily use. A box in the aircraft (the interrogator) sends short radio pulses to a beacon on the ground (the transponder). The beacon answers after a fixed delay, and the aircraft works out the distance from how long the answer took to come back [17][18]. The pilots see a distance in nautical miles. So "DME" can mean either end of the link, which is why the question of airborne or ground had to be settled first.

Several independent sources tie the name to the airborne box. A repair station lists "066-1019-ALL Bendix/King KDM 7000A DME Transceiver" and "KDM 7000B DME" [5]. A test-set maker sells a "KDM-7000 Test Set" that tests the KDM-7000, 7000A and 7000B [8]. Honeywell's parts catalog still carries KDM 7000B maintenance and installation manuals and circuit cards [6]. A 1977 maintenance manual for a King accessory calls the KDM 7000( ) a "digital ARINC 568 DME Interrogator" [2]. ARINC 568 is the airline standard for the airborne Mark 3 DME [22]. Confirmed

→ See the training certificate (companion page with the scanned certificate).

1.1 Candidates considered

Three possibilities were considered. Each was checked against sources rather than assumed.

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2. History: King Radio, Bendix/King, Allied-Signal, Honeywell

In briefEd King founded King Radio in 1959 and soon moved it to Olathe, Kansas [15][14]. The company was best known for light-aircraft radios but also built airline equipment, starting with the all-solid-state KTR 900 transceiver in 1966 [14]. The KDM 7000 existed by February 1977, when a maintenance manual for a King accessory named it [2]. Allied bought Bendix in 1983 and King Radio in 1983 or 1985 (sources differ), and the two were merged as Bendix/King [15][14]. In late 1988 a service bulletin and an FAA airworthiness directive required a fix to certain KDM 7000B units [1][3]. The line passed to Honeywell with the 1999 merger [16].

The introduction date of the KDM 7000 is not documented in anything found Not found. The 1977 CMM date is only the latest possible date for the basic model, and the letter suffixes (A, B) came later. The dates of the 7000A and 7000B are also unknown. The 1988 service bulletin is numbered -34-14, and a -34-12 also exists [1][7], If those numbers run in sequence, the 7000B had already collected a dozen or more bulletins by late 1988, which would suggest a unit several years into service. The numbering scheme is not confirmed, so treat this as a hint only. Inferred

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3. The units and how they connect

In briefA KDM 7000B installation is more than one box. The pilots tune the DME from the VHF NAV control panel: selecting a VOR or ILS frequency also selects the paired DME channel, and the DME and NAV receiver share the same channel-selection wires [1][22]. The KDM 7000B sits in the electronics bay, runs on 115 V ac 400 Hz aircraft power [12], and sends distance to the cockpit indicators as ARINC 568 digital data [2][22]. It talks to the ground through an L-band antenna on the underside of the fuselage [22][31]. Older aircraft wired for analog DME used a King 499 synchro driver to convert its output [2].

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4. How DME works

In briefDME measures distance by timing a radio echo that is answered, not reflected. The aircraft sends a pair of pulses; the ground station hears them, waits exactly 50 µs (on reply delay (50 or 56 µs).">X channels) and sends a pair back on a frequency 63 MHz away. The aircraft measures the total time, subtracts the 50 µs, and divides by about 12.36 µs for each nautical mile of distance there and back [17][19][20]. The result is the straight-line slant range to the station, not the distance over the ground [18].

4.1 Two-way ranging

FAA Order 6820.14 describes it this way: when the pilot or flight management computer selects a ground station, "the airborne interrogator sends out distance interrogation pulses on the receiving channel frequency assigned to the ground station." The ground station receives them, delays them "a fix[ed] amount," and transmits replies back on the assigned channel. Because radio travels at a known speed, the elapsed time gives the distance. "Timing circuits on the aircraft measure the time intervals between the interrogation and reply, subtract the 50 or 56 µs delay, and convert the remaining time difference to distance," which is then displayed or sent digitally to other equipment [17]. Confirmed

4.2 Pulse pairs, X and Y channels

DME never sends single pulses. Each interrogation and each reply is a pair of pulses a fixed time apart, and the spacing tells the receiver whether the pair is meant for it. Each pulse is about 3.5 µs wide [20]. There are two families of channels [17][19][20]:

X channels came first; Y channels were added later for more capacity [19]. Whether the KDM 7000B covered Y channels as well as X channels was not found in any source Not found.

4.3 The frequency plan and VOR/ILS pairing

DME uses the band from 960 to 1215 MHz [17][18]; the 252 assigned frequencies run from 962 to 1213 MHz in 1 MHz steps [19]. Aircraft always interrogate between 1025 and 1150 MHz. The ground station replies 63 MHz above or below the interrogation frequency, and which way depends on the channel [19][20][21]. Frequencies around 1030 and 1090 MHz are kept free because the air traffic control radar beacon system (SSR) uses them [19][21].

Pilots never select a DME channel number directly. Each DME channel is paired with a VHF VOR or ILS frequency, and tuning the VHF NAV frequency tunes the DME too [19][20]. Channels 17 to 56 pair with 108–112 MHz (odd tenths for ILS, even tenths for VOR) and channels 57–59 and 70–126 with VOR frequencies from 112 to 117.95 MHz; channels 1–16 and 60–69 are not paired with VHF NAV frequencies [20]. This pairing is why the KDM 7000B shares channel-selection wires with the NAV receiver, and why a fault in one could mis-tune the other (§8.4) [1][4].

4.4 Search, track, squitter and identification

Many aircraft use one ground station at once, and every aircraft hears every reply. To pick out its own replies, each interrogator sends its pulse pairs at deliberately irregular ("jittered") intervals. Only the replies to its own interrogations come back at a steady delay; replies meant for other aircraft arrive at random times [25][20]. In search mode the interrogator sends about 150 pulse pairs per second and looks for a delay that repeats. Once it finds one it locks on and drops to track mode at no more than about 30 pairs per second [19][20][21]. A King Radio patent notes that older designs took "from one to two seconds" to lock on [25].

The ground station also transmits squitter, pulse pairs not triggered by any interrogation, which keep its output steady and are ignored by aircraft because they are not synchronous with their interrogations [17][20]. About every 30 seconds the station keys its Morse identifier [17]. The DME ident tone is 1350 Hz, against 1020 Hz for the VOR or localizer, and is heard about once for every three or four VOR idents [18][19]. The station gives priority to the ident, then to distance replies, then to squitter [17]. A typical ground transponder can answer about 2,700 pulse pairs per second, enough for roughly 100 aircraft; beyond that it reduces receiver sensitivity so the most distant aircraft are dropped first [19][20].

4.5 Slant range, range and accuracy

DME measures the straight line from the aircraft to the station, which the AIM calls slant range. The AIM notes that the difference between slant range and ground distance "increases with aircraft altitude and proximity to the NAVAID" [18]. Far from the station the two are nearly the same; directly overhead, the DME reads roughly the aircraft's height above the station. Inferred

The AIM says reliable DME signals may be received out to 199 NM at line-of-sight altitude, with accuracy "better than 1/2 mile or 3 percent of the distance, whichever is greater" [18]. ICAO recommends an error no larger than 0.25 NM plus 1.25% of the distance [19][20]. FAA ground facilities are classed by standard service volume: Terminal (out to 25 NM, up to 12,000 ft), Low (40 NM, up to 18,000 ft) and High (up to 130 NM between 18,000 and 45,000 ft), plus newer DME Low and DME High volumes [18]. The ARINC 568 standard for the airliner's box adds 200 NM search-range limiting [22]. The KDM 7000B's own accuracy figure was not found Not found.

4.6 The ground end

The KDM 7000B is only half of the system. The ground station consists of a transponder, antenna, monitor and control unit. The monitor checks reply delay, reply efficiency, pulse spacing, pulse count, identification, radiated power, receiver sensitivity and transmitter frequencies. If a parameter goes out of limits, a single-transponder station shuts down and a dual station transfers to its standby equipment [17]. A typical en-route or terminal ground transponder has a 1 kW peak output [19]. DMEs are commonly co-located with a VOR (VOR/DME), an ILS (ILS/DME) or a TACAN (VORTAC) and share its identifier [19][20][18].

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5. Inside the KDM 7000B

In briefNo schematic, block diagram or internal photo of the KDM 7000B was found in public sources. What does survive is a list of its replaceable assemblies in Honeywell's parts catalog: numbered circuit cards (1, 3, 4 and 6 are listed), a VCO, buffer, divider-mixer, preselector, duplexer and IF board [6], plus a tuning mechanism sold by a parts dealer [13]. Those names outline a conventional DME transceiver, but the functions assigned to each card below are reasoned from the names, not from a King document. A 1980s King Radio patent shows how the company's engineers approached microprocessor DME design, but it is not confirmed to describe the KDM 7000B.

5.1 Cards and modules

Several of these assemblies are shared across the KDM 7000, 7000A and 7000B ("KDM7000/A/B"), while cards 1 and 3 have separate 7000B part numbers [6]. That suggests the three models share an RF section and differ mainly in the digital cards. Inferred The catalog descriptions are abbreviated and may not reflect how King's maintenance manual names the assemblies. The KDM 7000B maintenance manual (006-05155-0005) and the "KDM 7000B (521D)" manual (006-05164-0001) would settle these questions [6].

5.2 King Radio's DME design thinking (patent evidence)

King Radio held a series of DME patents. In 1966–1970 it filed for a digital distance-measuring method, a rapid-search technique, a DME indicator and a search/track decision circuit [26]. In 1981 King engineer James L. Stolpman filed for a microprocessor-based DME, granted in 1986 as US 4,599,617 [25].

The patent describes the problem any DME faces: the aircraft hears the replies to every aircraft using the station, so it must sort out which replies are its own. Older designs checked one reply per interrogation against a fixed-width range gate and took "from one to two seconds" to lock on. King's method stored every reply received after each interrogation. After a new channel was tuned, the unit made three interrogations before analyzing anything. It then compared each range figure from the latest interrogation with those from the previous seven, using a range gate whose width varied with the time between interrogations and with whether the unit was already locked. Statistical tests guarded against locking onto noise or squitter [25]. The circuit shown includes a microprocessor, a range counter and latch, RAM, a pair of shift registers for self-test, and an analog pulse-pair output for other equipment [25].

The patent comes from the same company and location and dates from 1981–1986, a few years before the KDM 7000B service bulletins of 1988. It is reasonable to read it as evidence of how King's DME engineers worked, but not as a description of the KDM 7000B. The KDM 7000 predates the patent's 1981 filing by at least four years [2], so the basic 7000 at least cannot have been designed around it. Inferred

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6. Variants and part numbers

In briefAll KDM 7000 models share the base part number 066-1019; the dash number identifies the variant and configuration [5][10][1]. Sources name four versions: KDM 7000, 7000A, 7000B and a "KDM 7000B (521D)" [6]. Australia's airworthiness directive lists six KDM 7000B dash numbers [1]. A Boeing 747 manual gives new dash numbers for units modified to cure the false-channeling problem [4]. One dealer lists -21 as a "KDM-7000," which conflicts with the CASA directive [11][1].

Bendix/King's own training grouped the models: the author's January 1993 course was titled "KDM 7000/A/B Digital DME Theory & Maintenance" [29], consistent with the shared "KDM7000/A/B" assemblies in the parts catalog [6]. What distinguished the three models is still not documented Not found.

6.1 Dash numbers

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7. Indicator, control panel and antenna

In briefThe KDM 7000B has no controls or display of its own for the crew; it is a "remote" box. The crew-facing parts are the NAV control panel (which tunes it) and the DME indicators (which show the distance). ARINC 568 sets out what those units should do [22]. King made DME indicators called the KDI 5710 and KDI 5700, whose manuals are still catalogued [6], and the KDI 5710 is the indicator a shop needs to bench-test a KDM 7000B [8]. The specific indicator, control panel and antenna models used with the KDM 7000B on any given aircraft were not found.

The Honeywell Bendix King catalog also lists other "DME INDICATOR" part numbers, but none of the entries found names the KDI 5710 or KDI 5700 or links them to the KDM 7000B, so they are not listed here Not found. The KDI 572, 573 and 574 indicators in the same catalog belong to King's general-aviation DME line [6]; no source connects them with the KDM 7000B.

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8. Operation and maintenance

In briefIn the air, the crew had little to do with the KDM 7000B: tuning a VOR or ILS frequency tuned the DME, and the distance appeared on the indicator. In the shop, Bendix/King specified test set 696-2795-00; Avionics Specialist, Inc. builds an equivalent (ASI-776-4) that combines the test set and pin-out panel and works with a DME signal generator and a KDI 5710 indicator [8]. The KDM 7000B's best-documented event is the late-1988 false-channeling fix: Bendix/King Alert SB KDM 7000B-34-14 and FAA AD 88-25-01 [1][3].

8.1 In the cockpit

Because DME channels are paired with VHF NAV frequencies, the crew tuned the DME by tuning the NAV receiver; the KDM 7000B followed on the shared channeling lines [1][20]. They confirmed the station by its Morse identifier, heard as a 1350 Hz tone [18]. The ARINC 568 features the unit was built to include a "memory" that holds distance through short signal gaps, a warning flag on failure, a functional test, and 200 NM search-range limiting with an override [22]. Which of these a KDM 7000B installation used, and what its front-panel test did, was not found. Not found

8.2 Shop test equipment

8.3 Manuals

These are current catalog listings; which editions were in use in 1989–1996 is not known. No manual text was available for this document. Not found

8.4 The 1988 false-channeling directive

The most serious documented problem with the KDM 7000B involved its connection to the NAV receiver. Because the DME and the VHF NAV receiver were tuned over the same, paralleled channeling lines, a failure in the DME or its power supply could pull those lines to the wrong state, so the NAV receiver selected a different frequency from the one set on the control panel [1]. The Boeing 747 AMM warns that this "could cause flight path deviations" [4]. In the worst case a crew could follow guidance from a station other than the one they had selected. Inferred

The AD came out in December 1988, just before the author's 1989–1996 period of radar and DME work began, and about four years before his January 1993 KDM 7000/A/B course [29]. Units still awaiting modification could have been passing through shops in the early 1990s. Inferred

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9. Specifications

In briefOnly a handful of KDM 7000B-specific specifications are available, almost all from one data plate seen in a seller's photo: 18.3 lb, 115 V ac 400 Hz at 0.5 A, TSO-C66a [12]. Performance figures such as transmitter power, receiver sensitivity and accuracy were not found. The table separates what is known about this unit from the general DME and ARINC 568 figures that any compliant unit had to meet.

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10. Firsthand notes

In briefThe author's firsthand material for this unit is his certificate for Bendix/King's "KDM 7000/A/B Digital DME Theory & Maintenance" course of January 18–22, 1993 [29], together with his 1989–1996 period of radar and DME work. The rest of this page is drawn from the cited sources, not from his memory of the work.

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11. Open research questions

In briefWhat the sources could not answer. The identity of the "7000B" is settled, and the author's January 1993 Bendix/King course certificate dates his training on it. The remaining gaps concern its internals and performance.

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12. Photos found elsewhere

In briefNo freely licensed photograph of a KDM 7000B was found. These pages have photos that are commercial or otherwise restricted, so they are linked rather than reproduced. Listings can disappear at any time.

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Glossary

In briefPlain-language definitions of the terms and abbreviations used in this document.

Airworthiness directive (AD)

A mandatory safety instruction from an aviation authority. FAA AD 88-25-01 and CASA AD/RAD/45 cover the KDM 7000B. [3][1]

AMM

Airplane maintenance manual: the aircraft manufacturer's manual for work on the aircraft, such as the Boeing 747 AMM chapter 34. [4]

ARINC 429

The later, widely used airliner data bus. Not the bus the KDM 7000B used (that was ARINC 568). [23]

ARINC 521D

An earlier airline DME standard with analog outputs. The King 499 synchro driver let an ARINC 568 KDM 7000 work in an aircraft wired for it. [2][22]

ARINC 568

The airline standard ("characteristic") for the Mark 3 airborne DME: box form factor, connectors, wiring, and a six-wire serial digital output of distance. King called the KDM 7000( ) a digital ARINC 568 interrogator. [22][2][23]

BCD

Binary-coded decimal: each decimal digit sent as a 4-bit code. ARINC 568 sends distance as serial BCD. [22]

Channeling

Selecting the DME channel. In the KDM 7000B installation the DME and VHF NAV receiver share paralleled channeling lines, the subject of AD 88-25-01. [1][4]

CMM

Component maintenance manual: the shop manual for one unit, organized by ATA chapter (34 for navigation). [2]

DO-160

RTCA's environmental test standard for airborne equipment. The data plate's "ENV CAT" string encodes the categories tested. [12]

Duplexer

A component that lets a transmitter and receiver share one antenna. The KDM 7000/A/B has a duplexer assembly. [6]

EE bay

Electrical and electronics equipment bay: the avionics compartment where remote units such as the KDM 7000B are installed. [4]

IF

Intermediate frequency: the fixed lower frequency a receiver converts signals to for amplification and detection. The KDM 7000/A/B has an IF board. [6]

ILS

Instrument landing system. DME channels are also paired with ILS localizer frequencies. [20][19]

Interrogator

The airborne half of DME: it sends pulse-pair interrogations and times the replies. The KDM 7000B is an interrogator. [17][4]

Jitter

Deliberately irregular spacing of interrogations, so each aircraft can recognize replies to its own interrogations among everyone else's. [25][20]

L band

The radio band around 1–2 GHz. DME (960–1215 MHz) sits at its lower end, alongside ATC transponders and TCAS. [17][19]

Preselector

A tuned filter ahead of a receiver that passes the wanted band and rejects strong out-of-band signals. A KDM 7000/A/B assembly. [6]

Pulse pair

Two pulses sent a fixed time apart (12 µs on X channels). DME always transmits in pairs; the spacing identifies the channel type. [17][20]

Range gate

A time window, centered on the expected reply time, in which a DME looks for its own replies. King's US 4,599,617 varies its width. [25]

Reply delay

The fixed time a ground station waits between receiving an interrogation and replying: 50 µs (X) or 56 µs (Y). The interrogator subtracts it. [17]

Service bulletin (SB)

A manufacturer's instruction to inspect or modify equipment. "Alert" bulletins address safety issues, such as SB KDM 7000B-34-14. [1]

Slant range

The straight-line distance from the aircraft to the ground station, which is what DME measures. It exceeds ground distance, most noticeably close to the station at altitude. [18]

Squitter

Pulse pairs a ground station transmits without being interrogated, keeping its output steady. Aircraft ignore them because they are not synchronous with their own interrogations. [17][20]

SSR

Secondary surveillance radar (ATC radar beacon system), which uses 1030 and 1090 MHz; DME assignments avoid those frequencies. [19][21]

Synchro

An electromechanical AC position transmitter/receiver used by older analog instruments. The King 499 "synchro driver" converted digital DME data for such installations. [2]

TACAN

The military tactical air navigation system; its distance function is compatible with civil DME. VOR + TACAN = VORTAC. [19][20]

Transponder (DME ground station)

The ground half of DME: it receives interrogations and replies after a fixed delay. Not to be confused with the aircraft's ATC transponder. [17]

TSO-C66

The FAA Technical Standard Order for airborne DME. The KDM 7000B plate says TSO C66a; the current revision, C66c, invokes RTCA DO-189. [12][24]

VCO

Voltage-controlled oscillator: an oscillator whose frequency is set by a control voltage, typically part of a frequency synthesizer. A KDM 7000/A/B assembly. [6]

VOR

VHF omnidirectional range: a ground beacon giving bearing. DME channels are paired with VOR frequencies, and many stations are VOR/DMEs. [18][19]

X and Y channels

The two families of 126 DME channels, differing in pulse spacing (X 12/12 µs, Y 36/30 µs) and reply delay (50 or 56 µs). [17][19][20]

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13. Image credits

In briefEvery image on this page is public-domain government or patent material, openly licensed material with a named author, or an original diagram drawn for this document. None shows an actual KDM 7000B; no commercial listing photos are embedded. The author's training certificate is shown on a separate companion page.

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14. References

In briefAll sources cited in the text. URLs were checked in September 2026.

1. [1]Civil Aviation Safety Authority (Australia), Airworthiness Directive AD/RAD/45, "King KDM 7000B Distance Measuring Equipment," issue 2/89 (applicability P/N 066-1019-21/-23/-26/-33/-43/-57, S/N 21855–22526; requires Bendix/King Alert Service Bulletin KDM 7000B-34-14 of 4 Nov. 1988; "FAA AD 88-25-01 refers"). https://services.casa.gov.au/airworth/airwd/ADfiles/equip/rad/rad-045.pdf
2. [2]Essco Aircraft, listing for "King Synchro Driver Assembly Part No. 499 Component Maintenance with Parts 34-50-01" (Pacific Electro Dynamics CMM, Feb. 1977; King manual P/N 006-5153-00, King P/N 068-1013). The listing describes the 499 as used with a "King Radio Model KDM 7000( ) digital ARINC 568 DME Interrogator to provide compatibility with an analog ARINC 521D DME." https://www.esscoaircraft.com/products/king-synchro-driver-assembly-part-no-499-component-maintenance-with-parts-34-50-01
3. [3]Air Research (airresearch.com), index of FAA appliance airworthiness directives, heading "Bendix/King": "88-25-01 Distance Measuring Equipment 12/20/88." https://www.airresearch.com/demo/appl.htm
4. [4]Boeing 747 Airplane Maintenance Manual, Chapter 34 (Navigation), DME section, as reproduced by aero.cn. Warning that KDM 7000/B interrogators must match part numbers in the AMM table, with an unmodified-to-modified part-number table and reference to Boeing SB 34A2308. Note: the page timed out when fetched for this document; the content was read from the search engine's indexed excerpt. http://www.aero.cn/2011/0320/21820_100.html
5. [5]Field Aviation East Ltd., Avionics Instruments and Components Capability List, report 400-068-90 Rev. 42 (lists 066-1019-ALL Bendix/King KDM 7000A "DME Transceiver" and KDM 7000B "DME"). https://fieldaero.com/Portals/0/ThemePluginPro/uploads/2024/4/25/400-068-90-r-42-avionics-instruments-and-components-capability-list.pdf
6. [6]Honeywell Bendix King Product Reference Catalog (CAGE 01KG6), as indexed by Aeroval: manuals on pp. 87, 88, 106 and 107; KDM 7000/A/B circuit-card and module entries on pp. 1025–1026 (link is p. 1025; change "pg=" for the other pages). https://aeroval.com/ref/?pg=1025&search=bendix
7. [7]Aeroval catalog entry 60007439-0020, "SB KDM 7000B-34-12" (Honeywell Bendix King service bulletin). https://aeroval.com/ref/2229324/60007439-0020/
8. [8]Avionics Specialist, Inc. (ASI), ASI-776-4 "KDM-7000 Test Set," equivalent Bendix/King P/N 696-2795-00; units tested KDM-7000, KDM-7000A, KDM-7000B. https://www.asitest.com/cgi-bin/Results.pl?CatalogIndex=2939
9. [9]LinAire LA-3009 test-panel harness cable list (as posted by Avionteq): cable "LD 8008 — Honeywell KDM 7000/A/B." http://www.avionteq.com/LinAire-LA-3009-Test-panel-harness-cable.aspx
10. [10]ILS Aviation Auctions listing, "066-1019-00 – D.M.E.," alternate part number KDM-7000. https://auction.ilsmart.com/Listing/Details/1702515/066101900-DME
11. [11]SE Aerospace, "066-1019-21 BendixKing KDM-7000" parts listing. https://www.seaerospace.com/sales/product/BendixKing/KDM-7000/066-1019-21
12. [12]Whaletail Sales, "KDM 7000B DME" listing ("from retired 737 aircraft"; text gives "PN:006-1019-27"), with four photos including the data plate. Photos are the seller's and are not reproduced here. https://whaletailsales.com/products/kdm-70008-dme
13. [13]Aircraft Parts Store, "P/N 076-00340-0001 – TUNING MEC KDM7000." https://aircraftpartsstore.com/shop/product/076-00340-0001
14. [14]Flying Tin editorial team, "Silver Crown: The History of King Radio," July 5, 2026 (includes a photo captioned "a KDM 7000B 521D DME with an 860E 2 Test rig"). https://www.flyingtin.com/industry/silver-crown-the-history-of-king-radio-4174/
15. [15]Wikipedia, "King Radio (company)." https://en.wikipedia.org/wiki/King_Radio_(company)
16. [16]Wikipedia, "AlliedSignal." https://en.wikipedia.org/wiki/AlliedSignal
17. [17]Federal Aviation Administration, Order 6820.14, Siting Criteria for Distance Measuring Equipment, Oct. 19, 2023, Chapter 2 "The DME System" (Figure 2-2 "DME Two-way Ranging Concept"; U.S. Government work). https://www.faa.gov/documentLibrary/media/Order/FAA_Order_6820.14.pdf
18. [18]Federal Aviation Administration, Aeronautical Information Manual, Chapter 1, Section 1, paragraphs 1-1-7 "Distance Measuring Equipment (DME)" and 1-1-8 "Navigational Aid (NAVAID) Service Volumes." https://www.faa.gov/air_traffic/publications/atpubs/aim_html/chap1_section_1.html
19. [19]Wikipedia, "Distance measuring equipment." https://en.wikipedia.org/wiki/Distance_measuring_equipment
20. [20]airnav.eu, "DME Infographics" (channel pairing table, pulse characteristics, X/Y spacing and delay table, search/track rates; cites ICAO Annex 10 Vol. I §3.5). http://www.airnav.eu/index.php?stranka=DMEen
21. [21]National Radio Astronomy Observatory, Electronics Division Internal Report 313 (DME band: air-to-ground 1025–1150 MHz, ground-to-air 962–1024 and 1151–1213 MHz; 150 pulse pairs/s search). https://library.nrao.edu/public/memos/edir/EDIR_313.pdf
22. [22]ARINC Characteristic 568, Mark 3 Airborne Distance Measuring Equipment (table of contents as published by Intertek Inform for Supplement 8; withdrawn 2013). https://www.intertekinform.com/en-au/standards/arinc-568-68-supp-8-98479_saig_arinc_arinc_207002/
23. [23]North Atlantic Industries, Model AR2 ARINC 568/582 interface description (six-wire serial bus; 32-bit words with an 8-bit label). https://www.naii.com/model/AR2
24. [24]RTCA DO-189 (1985), Minimum Operational Performance Standards for Airborne Distance Measuring Equipment (DME) Operating within the Radio Frequency Range of 960–1215 Megahertz (catalog listing). FAA TSO-C66c invokes DO-189. https://store.accuristech.com/standards/rtca-do-189?product_id=2200277
25. [25]J. L. Stolpman (assignee King Radio Corporation, Olathe, Kansas), U.S. Patent 4,599,617, "Method and apparatus for evaluating the range data accumulated by distance measuring equipment," filed Sept. 21, 1984 (continuation of an application filed June 19, 1981), issued July 8, 1986. https://patents.google.com/patent/US4599617A/en
26. [26]Earlier King Radio Corp. DME patents cited by US 4,599,617: US 3,412,400 "Method and apparatus for digitally measuring distance" (filed 1966, issued 1968); US 3,456,257 "…rapid search distance measuring equipment" (1967/1969); US 3,533,060 "Indicator for distance measuring equipment" (1966/1970); US 3,702,475 "Search-track decision circuit for distance measuring equipment" (1970/1972). Link is US 3,702,475. https://patents.google.com/patent/US3702475A/en
27. [27]Ingenium – Canada's Museums of Science and Innovation, artifact 2005.0212.001, King KDM 700 DME (data plate: P/N 066-1003-00, WT 11.4 lbs, TSO C66 Cat B, 14 V dc 5.5 A / 28 V dc 2.75 A). Museum image licence is non-commercial, so it is linked, not reproduced. https://collections.ingenium.ca/en/id/2005.0212.001/
28. [28]Precision Aero Technology (Precision Aviation Group), Commercial Capabilities catalog, Mar. 2024 (lists "2041167 (SERIES) DMA-37A DME XCVR, Honeywell," ATA 34, on 737, 747, 757, 767 and A320). https://www.precisionaviationgroup.com/wp-content/uploads/2024/03/PAT-Commercial-Catalog.pdf
29. [29]Course completion certificate: "KDM 7000/A/B Digital DME Theory & Maintenance," presented by Bendix/King, Allied-Signal Aerospace Company, January 18–22, 1993 (form 058-02638-0001). Issued to the author; scan from the author's personal collection, supplied September 2026. Primary source; not published online.
30. [30]Wikimedia Commons, "Inside of a Boeing 737-200 cockpit (Canadian North Airlines C-GDPA).jpg," photo by Quintin Soloviev, Oct. 17, 2024, CC BY 4.0. https://commons.wikimedia.org/wiki/File:Inside_of_a_Boeing_737-200_cockpit_(Canadian_North_Airlines_C-GDPA).jpg
31. [31]Wikimedia Commons, "Jet-liner's antennas.PNG," drawing by Tosaka, Apr. 20, 2010, CC BY-SA 3.0 (legend item 5 = DME). https://commons.wikimedia.org/wiki/File:Jet-liner%27s_antennas.PNG
32. [32]Wikimedia Commons, "DCA-VOR-DME.jpg," photo by MediaGuy768, Dec. 1, 2023, CC BY-SA 4.0. https://commons.wikimedia.org/wiki/File:DCA-VOR-DME.jpg

Written by Rick Childers, September 2026, for GeeksForge Research Projects. Firsthand material: the author's January 1993 training certificate and his 1989–1996 dates. Specifications are quoted from the sources shown; where sources disagree, both values are given.