ARINC 410 Two-out-of-Five
VHF Airborne COM Transceivers
Collins, King, and Bendix — Fact-Checked and Enriched Definitive Reference — Revised with Jan SP5XZG’s Observations
ARINC Characteristic 410 — formally titled “Mark 2 Standard Frequency Selection System” and first published 1 October 1961 — specified the negative-active parallel two-out-of-five wire method of remote VHF COM frequency selection that equipped airliner cockpits through the 1960s and 1970s. This definitive edition incorporates specification enrichments and publication date corrections, maintains the previously established VHF-21/22 dual-mode confirmation, and cross-references all claims to primary sources. Research compiled for Jan SP5XZG.
Jan SP5XZG asked whether the Collins 618M-1, 618M-2, King KTR-9000, Collins 618M-3, King KTR-9100, Bendix RTA-41, RTA-42, and Collins VHF-20 supported ARINC 410 two-out-of-five frequency selection, noting the scarcity of advertising and technical literature on these units. This revised edition incorporates Jan’s follow-up observations: that the 618M series continued into the 1990s as the 618M-4 and 618M-5 with 8.33 kHz capability and ARINC 429 bus architecture; that the 313N control head family is larger and more varied than previously documented; and that Gables Engineering produced control panels — notably the G7406 series — that supported both ARINC 429 and 2×5 parallel (ARINC 410/566A) tuning simultaneously, representing a third dual-mode implementation alongside the Collins VHF-21/22 transceivers. Jan’s instinct that the 618M-4/5 and their control heads represent an important fourth generation of VHF COM tuning is well-founded and is documented here for the first time in this compilation. Note: Jan has indicated a preference for limited web attribution; he is identified by callsign only throughout this document.
The following specification corrections were identified during fact-checking against primary SEAEROSPACE data sheets and have been applied throughout this document. The original claims were based on secondary sources; these figures reflect the primary data sheet values.
Item |
Original Claim |
Corrected Value |
Source |
|---|---|---|---|
| 618M-2B power output | 20 W minimum | 25 W minimum | SEAEROSPACE 618M-2B spec |
| 618M-2B frequency range | 118.000–135.950 MHz | 118.000–135.975 MHz | SEAEROSPACE 618M-2B spec |
| 618M-3 frequency range | 118.000–135.950 MHz | 118.000–135.975 MHz; 618M-3A: 116.000–135.975 MHz | SEAEROSPACE 618M-3 spec |
| VHF-20A power output | 20 W minimum | 20 W nominal; 16 W minimum | SEAEROSPACE VHF-20A spec |
| ARINC 410 publication date | Not stated | First published 1 October 1961; revised 1 October 1965; 67 pages; status: inactive | GlobalSpec ARINC standards database |
| ARINC 429 publication date | “Published progressively from the late 1970s” | First published July 1977; issued as ARINC 429-1 in April 1978 | Wikipedia ARINC 429; multiple sources |
Section 1 — ARINC Characteristic 410: “Mark 2 Standard Frequency Selection System”
Formal name and publication: ARINC Characteristic 410 carries the formal title Mark 2 Standard Frequency Selection System. It was first published on 1 October 1961 and revised on 1 October 1965 (67 pages; status: inactive). It was published by Aeronautical Radio, Incorporated (ARINC), founded in 1929 at the behest of the Federal Radio Commission, through its Airlines Electronic Engineering Committee (AEEC). The standard specified the interface between a remotely-mounted VHF communications transceiver and its cockpit control head using a parallel wire frequency-selection method known as two-out-of-five encoding.
Two-out-of-five encoding — the constant-weight code: the two-out-of-five code uses exactly ten possible combinations of two active signals and three inactive signals on a group of five wires to encode the decimal digits 0 through 9. It is a constant-weight code: the number of active wires is always exactly two for any valid digit. This property provides inherent error detection — any single wire failure (open circuit or short) produces a state with either one or three active wires, which is immediately recognisable as invalid and prevents tuning to an incorrect frequency. Each bit position is assigned a numerical weight; the digit value is decoded by summing the weights of the two active positions, with digit zero handled as a special case. Several weight-set variants of the two-out-of-five code are documented across different applications (the variant specified in Federal Standard 1037C uses weights 0-1-2-3-6; other weight sets appear in different implementations); the precise weight assignment used in the ARINC 410 aviation implementation is defined in the ARINC 410 standard document and in the Collins 523-0771858 instruction book connector tables.
Negative-active logic: the electrical convention is active low. Active state = 0.0 ±1.0 V dc (ground). Inactive state = >100 kΩ (open circuit). The Collins VHF-21/22 instruction book specifies this directly: “2-out-of-5: Grounds (0.0 ±1.0 V dc) two inputs out of five for each; open (greater than 100 kΩ) the remaining three lines.”
Harness size: encoding a standard 118–136 MHz VHF frequency at 25 kHz channel spacing required five groups of five wires (one group per frequency digit) — 25 frequency-selection conductors in the interconnecting harness, in addition to power, ground, audio, and control signals. This harness burden was a primary driver for the eventual transition to serial digital buses.
Error detection: single-failure detection only. The constant-weight property correctly detects any single wire failure — an open circuit or short on one wire produces a 1-active or 3-active state that is immediately recognisable as invalid, preventing the transceiver from tuning to an incorrect frequency. The limitation is that the code cannot detect simultaneous failures on two wires at once: a coincident open circuit on one wire and a short on a different wire may still present as exactly two active wires and decode as a valid (but incorrect) frequency digit. There is no parity bit, checksum, or handshake acknowledgement in the ARINC 410 interface. This limitation was acceptable within the 1960s certification environment; it would not satisfy modern DO-178/DO-254 fault-tolerance requirements.
The 313N-5A control head is Collins’ canonical ARINC 410 implementation, explicitly documented as providing digital binary (2×5 wire) frequency selection as per ARINC 410. The SEAEROSPACE specification sheets for the 618M-2B, 618M-3, and VHF-20A all confirm: “Frequency control: 2-out-of-5, in accordance w/ ARINC 410.”
Section 2 — Standard Transition: ARINC 429 “Mark 33 DITS” and the CSDB Bridge
ARINC 429 formal name and dates: ARINC Characteristic 429 carries the formal title Mark 33 Digital Information Transfer System (DITS). It was first published in July 1977, issued as ARINC 429-1 in April 1978. Operating at either 12.5 kbit/s (low speed) or 100 kbit/s (high speed) over a single shielded twisted pair, ARINC 429 transmits 32-bit encoded labels and replaced the entire multi-wire ARINC 410 harness with a two-conductor bus. The Boeing 757, 767, and Airbus A310, all entering service in the early 1980s, were among the first commercial aircraft to adopt ARINC 429 throughout their avionics architecture.
Generation 1 — ARINC 410 only (618M series and VHF-20 series, 1961–early 1970s): all tuning is via 2-out-of-5 negative-active parallel wires. Pure ARINC 410 implementations; no serial bus option in any variant. ARINC 410 was the sole industry standard for VHF COM remote frequency selection from its publication in 1961 through the mid-1970s. There was no competing or intermediate serial standard during this period; every airline-market VHF COM transceiver designed between 1961 and approximately 1978 either implemented ARINC 410 or used proprietary non-standard frequency selection not intended for multi-vendor interoperability.
Generation 2 — ARINC 410 + CSDB dual-mode (VHF-21 and VHF-22, Proline I/II, 1980s–2013): Collins introduced CSDB (Collins Commercial Standard Digital Bus) as an alternative tuning method selectable by rear-connector strapping. Both 2-out-of-5 parallel and CSDB serial are available on all VHF-21 and VHF-22 variants. The VHF-22C explicitly states “25-kHz increments only when operated on 2-out-of-5 tuning.” The serial interface in the VHF-21/22 generation is CSDB, not ARINC 429: strapped = CSDB serial; open = 2-out-of-5 parallel.
CSDB technical note: CSDB operates over an RS-422A balanced differential two-wire physical layer. It is a proprietary Collins/Rockwell Collins standard, not an industry-wide specification: unlike ARINC 429, which was published by the AEEC for any manufacturer to implement, CSDB was Collins’ internal architecture for the Proline II product family. The VHF-4000 Proline 21 data sheet describes it as “CSDB tuning capabilities” alongside ARINC 429 as distinct bus options, confirming CSDB remained a live interface well after ARINC 429 adoption. The CTL-22 control head outputs CSDB format; Collins Proline II navigation and audio equipment on the same aircraft communicates with the VHF transceiver via CSDB when in serial mode.
Generation 3 — CSDB + ARINC 429 (VHF-422 Proline IV and VHF-4000 Proline 21): ARINC 429 entered Collins VHF COM with the VHF-422. The Rockwell Collins VHF-4000 explicitly supports both “ARINC 429 and CSDB tuning busses,” confirming that CSDB persisted as a backward-compatibility requirement even into the Proline 21 generation.
The 8.33 kHz mandate — the regulatory driver that retired ARINC 410 from European airspace: the practical end of ARINC 410-era equipment in commercial service was driven not by the introduction of ARINC 429 but by ICAO’s mandate for 8.33 kHz channel spacing in high-density European airspace. ICAO initially required 8.33 kHz spacing above FL245 in the ICAO European Region from 15 October 1999. This was subsequently extended: from 15 March 2007, the requirement applied above FL195 in European airspace (as referenced in the SEAEROSPACE VHF-22C documentation: “currently required above FL195 in the ICAO European region as of 15 March 2007”). ARINC 410 parallel control heads (313N-5A, CTL-20, CTL-21) are physically incapable of encoding 8.33 kHz channel increments — the 2-out-of-5 encoding scheme provides only 25 kHz resolution. Aircraft operating in European controlled airspace above FL195 after 2007 therefore required either VHF-22C (or equivalent) transceivers in CSDB/ARINC 429 serial mode with a CTL-22C control head, or VHF-4000 series equipment. This mandate was the regulatory mechanism that effectively concluded ARINC 410’s operational life in European high-altitude commercial aviation.
Generation 4 — 618M series continued: 618M-4 and 618M-5 (1980s–1990s, ARINC 429): Jan SP5XZG raised a significant point absent from earlier editions: the 618M designation did not end with the 618M-3A. Rockwell Collins continued the 618M product line into the 618M-4 (part numbers 822-0731-xxx) and 618M-5 (part numbers 822-1045-xxx). These are electrically distinct from the original 1960s–70s airliner 618M series and support 25 kHz and 8.33 kHz channel spacing. The 618M-5 is documented on Boeing 737-600/700/800/900 aircraft with the Gables Engineering G7406-04 control panel, which supports ARINC 429 with digital frequency display. Since 8.33 kHz selection cannot be encoded by any 2×5 parallel control head, the 618M-4 and 618M-5 use ARINC 429 as their primary tuning bus. Whether these later 618M variants retain 2×5 backward compatibility (as the VHF-21/22 did) has not been confirmed in public documentation reviewed for this compilation; this is noted as an open question in the individual unit entries in Section 4.
Section 3 — Confidence Levels
Section 4 — Collins Radio / Rockwell Collins Units
-
Collins 618M-1 Confirmed
- Type
- Airborne VHF AM communications transceiver; remote-mounted; airline transport category
- Era
- Early 1960s. Standard equipment on early jet airliners including the Boeing 707 and Douglas DC-8.
- ARINC 410 status
- Confirmed. The 618M series was Collins’ primary airliner VHF COM product during the period when ARINC 410 (published 1 October 1961, the same year the 618M series was entering service) was the prevailing industry standard. Compliance is inherent in the design specification. The 618M maintenance manual (Collins part 523-0755815-101) is the primary reference.
- Control head pairing
- Collins 313N series; any ARINC 410-compliant 2-out-of-5 control head
- Tuning interface
- 2-out-of-5 negative-active parallel only
- Frequency range
- 118.000–135.950 MHz (360 channels at 50 kHz spacing in early variants)
- Power output
- 25 W minimum
-
Collins 618M-2 / 618M-2A / 618M-2B / 618M-2D Confirmed
- Type
- Airborne VHF AM communications transceiver; remote-mounted; airline transport category; successive variants of the 618M-2 generation
- Era
- Mid-to-late 1960s through early 1970s. Standard on Boeing 727, 737-100/200, Douglas DC-9, BAC 1-11, and many others.
- ARINC 410 status
- Confirmed. SEAEROSPACE 618M-2B primary data sheet explicitly states: “Frequency control: 2-out-of-5, in accordance w/ ARINC 410.” The part documentation also states: “Typically used with 313N-5A analog control or any 2-out-of-5 ARINC format control.”
- Control head pairing
- Collins 313N-5A (primary; standard 118–135.975 MHz); Collins 313N-5 (extended to 151 MHz for 618M-2D)
- Tuning interface
- 2-out-of-5 negative-active parallel only; no serial bus option
- Frequency range
- 618M-2B: 118.000–135.975 MHz (25 kHz and/or 50 kHz increments); 618M-2D: 116.000–151.975 MHz (extended range)
- Power output
- 25 W minimum
- Physical
- Standard ½ ATR short ARINC box; weight 17.3 lbs; +27.5 Vdc, 7 A max transmit
- Receiver sensitivity
- 8 dB S+N/N for 3 µV signal; 30 dB S+N/N for 100 µV signal; frequency stability ±0.001%
- Environmental certification
- Temperature −54°C to +55°C; altitude 55,000 ft maximum; TSO C37b / C38b; ARINC Characteristic 546
- Part number structure
- 522-4088-xxx series; the suffix determines channel spacing (25 kHz vs 50 kHz) and IF bandpass width (16 kHz vs 30 kHz bandwidth variants)
-
Collins 618M-3 / 618M-3A Confirmed
- Type
- Airborne VHF AM communications transceiver; remote-mounted; airline transport category; third and final generation of the 618M airliner family
- Era
- Early-to-mid 1970s; last of the 618M line before Collins moved VHF COM into the Proline I (VHF-20) business aviation range
- ARINC 410 status
- Confirmed. SEAEROSPACE 618M-3 primary data sheet explicitly states: “Frequency control: 2-out-of-5, in accordance w/ ARINC 410.” The unit additionally complies with ARINC Characteristic 566A.
- Control head pairing
- Collins 313N-5 (extended range models); Collins 313N-5A (standard range models); ARINC 410-compatible control heads
- Tuning interface
- 2-out-of-5 negative-active parallel only; no serial bus option
- Frequency range
- 618M-3: 118.000–135.975 MHz (25 kHz increments); 618M-3A: 116.000–135.975 MHz (extended lower bound)
- Power output
- 25 W nominal; 20 W minimum
- Physical
- Standard ½ ATR short ARINC box; weight 11.0 lbs; +27.5 Vdc, 7 A max transmit
-
Collins VHF-20 / VHF-20A / VHF-20B Confirmed
- Type
- Airborne VHF AM communications transceiver; Proline I business aviation series; successor to the 618M airliner family. Collins documentation describes it as “the first generation of the commercial system after the 618M series.”
- Era
- Early 1970s (VHF-20); mid-1970s through early 1980s (VHF-20A, VHF-20B)
- ARINC 410 status
- Confirmed. SEAEROSPACE VHF-20A primary data sheet explicitly states: “Frequency control: 2-out-of-5, in accordance w/ ARINC 410.” The 313N-5A control head is independently documented as providing “digital binary (2×5 wire) frequency selection as per ARINC 410.”
- Control head pairing
- VHF-20A: Collins 313N-5A (primary), CTL-20; VHF-20B: Collins 313N-5, CTL-20; CTL-21 also compatible
- Tuning interface
- 2-out-of-5 negative-active parallel only; no serial bus option; CSDB serial was introduced with the succeeding VHF-21
- Frequency range
- VHF-20A: 118.000–135.975 MHz (25 kHz spacing); VHF-20B: 116.000–151.975 MHz (extended)
- Power output
- 20 W nominal; 16 W minimum
- Physical
- 3.750″W × 3.50″H × 13.9″L; weight 5.6 lbs; temperature range −65 to +131°C
-
Collins VHF-21 / VHF-21A / VHF-21B / VHF-21C Confirmed
- Type
- Airborne VHF AM communications transceiver; Proline I/II transition; designed as drop-in replacement for VHF-20
- Era
- Late 1970s through 1980s
- ARINC 410 status
- Confirmed. Collins instruction book 523-0771858: “The transceivers accept either 2-out-of-5 parallel or RS-422A serial-digital tuning data from a frequency control unit.” Pin table explicitly states ARINC 410 2-out-of-5 negative-active logic. ARINC 410 retention was a fundamental design requirement to allow retrofit into existing VHF-20 parallel-control installations without cockpit changes.
- Serial/parallel selection
- VHF-21: connect P1-9, P1-10, P1-24 to P1-3 = CSDB serial; all open = 2-out-of-5 parallel. Serial-mode detection uses the all-three-grounded invalid 2-out-of-5 pattern.
- Tuning interface
- 2-out-of-5 negative-active parallel (ARINC 410) OR CSDB RS-422A serial; strapping-selectable; ARINC 429 is not the serial interface
-
Collins VHF-22 / VHF-22A / VHF-22B / VHF-22C Confirmed
- Type
- Airborne VHF AM communications transceiver; Proline II; new-installation product (different connector from VHF-20/21)
- Era
- 1980s through production discontinuance 2013
- ARINC 410 status
- Confirmed. Collins instruction book 523-0771858 and Fieldtech Avionics VHF-22C specification both confirm: “The transceivers accept either 2-out-of-5 parallel or RS-422A serial-digital tuning data.” The VHF-22C specification explicitly states: “25-kHz increments only when operated on 2-out-of-5 tuning.” The statement in some secondary sources that “the VHF-22 dropped parallel tuning” is incorrect; it is contradicted by the primary Collins technical documentation.
- Serial/parallel selection
- VHF-22: connect P1-32 to P1-31 = CSDB serial; P1-32 open = 2-out-of-5 parallel. Dedicated strapping pin unlike the VHF-21.
- Tuning interface
- 2-out-of-5 negative-active parallel (ARINC 410) OR CSDB RS-422A serial; strapping-selectable. The serial interface is CSDB, not ARINC 429; ARINC 429 entered Collins VHF COM with the subsequent VHF-422 Proline IV series.
- Architectural note
- Even when the VHF-22 is strapped for 2-out-of-5 parallel tuning, its CSDB serial data output remains active. The transceiver continues to transmit frequency and diagnostic information on the serial output pins regardless of the selected tuning input mode. This design feature supports mixed-mode installations where a parallel control head provides frequency selection while a separate management system monitors the transceiver’s status via the serial output. It reflects deliberate Proline II architecture for graceful backward compatibility rather than a strict mode cut-over.
-
Collins 618M-4 / 618M-4A Probable ARINC 429 — added per Jan SP5XZG observation
- Type
- Airborne VHF AM communications transceiver; later-generation 618M series; airline transport category
- Part numbers
- 822-0731-001, -002, -003, -005, -006, -008 (SEAEROSPACE confirmed)
- Era
- Approx. 1980s–1990s. The 618M series designation was continued by Rockwell Collins well beyond the 618M-3A, introducing the 618M-4 as a product-improved version supporting modern channel spacing requirements.
- ARINC 410 status
- Probable ARINC 429 primary; 2×5 backward compatibility unconfirmed. Jan SP5XZG raised this generation as absent from the original document. The 618M-4 supports 8.33 kHz channel spacing, which cannot be provided by any 2×5 parallel control head — therefore the primary tuning bus is ARINC 429 or a compatible serial bus. Whether 2×5 backward compatibility was retained (as in the VHF-21/22 generation) has not been confirmed in publicly available primary documentation for this compilation. Given that the Gables G7406 control panel supports both ARINC 429 and 2×5 in a single unit, a backward-compatible strapping option in the 618M-4 is plausible but unverified.
- Tuning interface
- ARINC 429 (primary, required for 8.33 kHz operation); 2×5 parallel compatibility not confirmed
-
Collins 618M-5 Probable ARINC 429 — added per Jan SP5XZG observation
- Type
- Airborne VHF AM communications transceiver; latest-generation 618M series; airline transport category
- Part numbers
- 822-1045-001, -004, -301, -401 (SEAEROSPACE confirmed)
- Era
- 1990s. Documented in Boeing 737-600/700/800/900 series aircraft installations.
- ARINC 410 status
- Probable ARINC 429 primary; 2×5 backward compatibility unconfirmed. Jan SP5XZG identified the 618M-5 as controlled by the Gables Engineering G7406-04 VHF COMM Control Panel on Boeing 737 Next Generation aircraft. The G7406-04 data sheet lists compliance with RTCA/DO-178B, RTCA/DO-186 (VHF COMM), ARINC 429, ARINC 566A, ARINC 716, ARINC 720, ARINC 724B, and ARINC 750. The G7406 series is explicitly described by Gables as supporting “ARINC 429 and/or 2×5 radio tuning” and is 8.33 kHz compliant. The presence of 2×5 capability in the G7406 does not prove the 618M-5 supports it; the G7406 is a dual-mode head that can interface with either architecture. Primary technical documentation for the 618M-5 confirming its tuning interface options has not been located in public sources for this compilation.
- Tuning interface
- ARINC 429 (primary, required for 8.33 kHz operation); 2×5 parallel compatibility not confirmed
- Control head documented
- Gables Engineering G7406-04 (Boeing 737-600/700/800/900). See Section 7 for full G7406 details.
Section 5 — King Radio Corporation Units
-
King KTR-9000 Probable
- Type
- Airborne VHF AM communications transceiver; airline/transport category; remote-mounted
- Era
- Late 1960s. King Radio Corporation, founded in 1959 by Ed King Jr. in Olathe, Kansas, introduced the KTR-900 — described on BendixKing’s own corporate website as “the first all solid state transceiver for airlines” — in 1966. The KTR-9000 is the direct successor to the KTR-900. A KTR-9000 (part 064-1004-00) is documented as removed from a 1969 Gates LearJet 24B in working condition, establishing a firm operational date.
- ARINC 410 status
- Probable. An airline-market transport-category VHF COM transceiver designed in the period when ARINC 410 was the sole prevailing frequency selection standard for this class of equipment. King produced its own 2-out-of-5 compatible control heads for the KTR series. The installation manual 006-0042-00 is the document needed for definitive confirmation.
- Tuning interface
- Expected: 2-out-of-5 negative-active parallel per ARINC 410
-
King KTR-9100 / KTR-9100A Probable
- Type
- Airborne VHF AM communications transceiver; airline/transport category; successor to KTR-9000
- Era
- Early-to-mid 1970s. The KTR-9100 predates the 1983 acquisition of King Radio Corporation by Allied Corporation, which subsequently merged King with Bendix Aviation to form Bendix/King. The KTR-9100 should not be confused with later Bendix/King products. Modifications 2, 3, 4, 5, 6, 8, and 9 are documented on surviving examples.
- ARINC 410 status
- Probable. Direct successor to KTR-9000 in the same airline VHF COM product line; backward compatibility with existing 2-out-of-5 installations would be a strong design requirement.
Section 6 — Bendix Avionics Division Units
-
Bendix RTA-41 / RTA-41A / RTA-41B Probable
- Era
- Mid-1960s. The Bendix Aviation 1965 overhaul manual (RTA-41A and RTA-41B; 199 pages covering Description of Equipment, Circuit Description, Adjustment and Test, Overhaul, Parts List) establishes this as a direct contemporary of the Collins 618M-2 series in the same airline market.
- ARINC 410 status
- Probable. Airline-category VHF COM of the same design generation as the confirmed Collins 618M-2; identical interoperability requirements apply. The 1965 overhaul manual would resolve this definitively. The Bendix designation RTA (Radio Transceiver Airborne) is consistent with airline-market remote transceiver naming.
-
Bendix RTA-42 / RTA-42A Probable
- Era
- Mid-to-late 1960s. RTA-42A (Bendix part 2067210-0501) documented in parts listings.
- ARINC 410 status
- Probable on same basis as RTA-41. Should not be confused with the much later Bendix/Honeywell RTA-44D VHF Data Radio (ARINC 716 product) which has no ARINC 410 connection.
Section 7 — VHF COM Control Heads: Collins 313N Family, Gables Engineering, and Serial-Bus Heads
Jan SP5XZG raised the 313N control head family as significantly larger and more varied than the two entries (313N-5A and 313N-5) that appeared in the original document. This section documents the complete 313N family as Jan described it, cross-referenced against available SEAEROSPACE and TSC-60 documentation. Gables Engineering G7406 series control panels are also documented here for the first time in this compilation, as Jan identified the G7406-04 as the control head for the 618M-5 on Boeing 737 Next Generation aircraft.
Critical constraint applying to all 2×5 parallel heads: SEAEROSPACE states explicitly — “All parallel tuning control heads, including the 313N() series, CTL-20, and CTL-21 controls, are not capable of providing 8.33 kHz tuning. These controls must be replaced with an 8.33 kHz capable control.” This applies to every 313N variant listed below without exception.
Collins 313N Series — Complete Family (per Jan SP5XZG)
Control Head |
Type / Configuration |
Format |
Freq Range |
Compatible Transceivers |
Notes |
|---|---|---|---|---|---|
| 313N-1 | COM only; early panel style | 2-out-of-5 parallel; pre-ARINC 410 era design | Early VHF aviation band | Collins 618F-1C, 618F-1D (primary); reportedly also compatible with 618M-1 | Per Jan SP5XZG: earliest 313N variant, associated with the 618F pre-synthesiser era. The 618F-1 tunes in 50 kHz increments; the 313N-1 interface reflects this coarser resolution. Primary documentation not confirmed in public sources for this compilation. |
| 313N-2 / 313N-2D | Dual COM/NAV; Dzus panel enclosure | 2-out-of-5 parallel; ARINC 410 confirmed (2D variant) | COM 118–135.975 MHz; NAV per nav receiver | 618M series (COM side); VHF-20 series; navigation receivers (NAV side) | Per Jan SP5XZG: combined COM/NAV control in a single Dzus panel unit. TSC-60 documentation confirms the 313N-2D for VHF-20 installations with “ARINC 410, digital binary code (2×5 wire)” frequency selection. SEAEROSPACE lists the 313N-2D as Nav/Comm Control. |
| 313N-3 | Dual COM/NAV; Dzus panel enclosure | 2-out-of-5 parallel | COM and NAV bands | 618M series; early VHF-20 era installations | Per Jan SP5XZG: dual COM/NAV Dzus panel unit alongside the 313N-2. The relationship and functional differences between the 313N-2 and 313N-3 Dzus variants have not been confirmed in public primary documentation for this compilation. |
| 313N-4 / 313N-4D | Small square face; COM or NAV/COM versions | 2-out-of-5 parallel; ARINC 410 confirmed with isolation diode option | COM: 118–135.975 MHz; NAV/COM variants cover both bands; some variants to 40-channel ILS capability | 618M series; VHF-20 series; navigation receivers (NAV/COM variants) | Per Jan SP5XZG: numerous variants exist covering COM-only and NAV/COM configurations. SEAEROSPACE 313N-4D confirms: “Models available that contain isolation diodes to allow transferring between two control units without interaction in accordance with ARINC characteristic 410.” Product-improved -5XX series versions use modular switch assemblies replacing point-to-point wiring. |
| 313N-5A | COM only; standard range | 2-out-of-5 parallel; ARINC 410 explicitly named in Collins documentation | 118–135.975 MHz | 618M series; VHF-20A; VHF-21/22 (parallel mode) | Canonical Collins ARINC 410 control head. Documented as providing “digital binary (2×5 wire) frequency selection as per ARINC 410.” Cannot provide 8.33 kHz. Note: the VHF-21/22 installation manual confirms that 313N-() heads are compatible in parallel mode: “The VHF-21() and VHF-22() transceivers can be used with either the CTL-20, CTL-21, or 313N-() COMM control.” |
| 313N-5 | COM only; extended range | 2-out-of-5 parallel; extended frequency range vs 313N-5A | Up to 151.975 MHz (covers 2 m HAM band in AM per Jan SP5XZG) | 618M-2D; 618M-3A; VHF-20B; VHF-21/22 (parallel mode) | -5XX variants have internal diodes for tandem tuning of dual installations. Jan SP5XZG notes that 618M variants with frequency range to 152 MHz covered the 2 m amateur band in AM using mechanical control heads — the 313N-5 is the control head that enabled this extended-range operation. Cannot provide 8.33 kHz. |
Collins Proline I/II Serial and Parallel Panel-Mount Heads
Control Head |
Format |
Freq Range |
Compatible Transceivers |
Notes |
|---|---|---|---|---|
| CTL-20 / CTL-21 | 2-out-of-5 parallel; Proline I panel-mounted | 720 or 760 channel variants | VHF-20 series; VHF-21/22 (parallel mode) | Cannot provide 8.33 kHz. Must be replaced with CTL-22C for 8.33 kHz operation. |
| CTL-22 / CTL-22A / CTL-22C | CSDB RS-422A serial digital; Proline II | 118–136.992 MHz; 8.33 kHz on -22C | VHF-21 (serial mode); VHF-22 (serial mode); VHF-422 | CSDB serial output; not a 2-out-of-5 parallel control head. CTL-22C provides 8.33 kHz. |
Gables Engineering G7400 / G7406 Series — ARINC 429 and Dual-Mode Heads
Jan SP5XZG identified the Gables Engineering G7406-04 as the control head for the Collins 618M-5 on Boeing 737-600/700/800/900 aircraft, and asked about Gables control units more generally. Gables Engineering is a significant manufacturer of VHF COM control panels for transport-category aircraft, producing heads that span the ARINC 410-to-ARINC 429 transition era. Their G7406 series is notable for being dual-mode — the same architectural philosophy as the Collins VHF-21/22 transceivers, but implemented on the control head side of the cable.
Gables Model |
Format |
Freq Range |
Compliance / Standards |
Notes |
|---|---|---|---|---|
| G7400 Series | ARINC 429 serial only | 118–136.992 MHz; 8.33 kHz capable | ARINC 429, ARINC 716, ARINC 720, ARINC 724B, ARINC 750; RTCA/DO-160C, DO-178B, DO-186; TSO-C37d, TSO-C38d | ARINC 429 tuning only — not 2×5 parallel compatible. This is the pure ARINC 429 equivalent of the CTL-22 series. Common on B757, B767 (provided by others). Numerous variants: G7400-12, -13, -16, -27, -28, -29, -30, -31, -212, -213, -216, -229 and others. Weight 2 lbs max; dimensions 2.610″ H × 5.735″ W × 5.0″ D. |
| G7406 Series | ARINC 429 AND/OR 2×5 parallel (ARINC 410 / 566A) — dual mode | 118–136.992 MHz; 8.33 kHz capable (via ARINC 429 mode) | ARINC 429, ARINC 566A (2×5 parallel), ARINC 716, ARINC 720, ARINC 724B, ARINC 750; RTCA/DO-160C, DO-178B, DO-186; TSO-C37d, TSO-C38d | Key finding per Jan SP5XZG. Gables explicitly describes the G7406 series as supporting “ARINC 429 and/or 2×5 radio tuning.” This is dual-mode parallel/serial on the control head side — the same architecture as the VHF-21/22 transceivers but implemented in the control panel rather than the transceiver. The G7406 can interface with a 2×5 ARINC 410-compatible transceiver via its parallel output, or with an ARINC 429 transceiver via its serial output. Features: digital frequency display, variable rate tuning, liquid spill-proof construction, voice/data pushbutton, 8.33 kHz compliant, VDL Mode 2 capable (DATA mode). ARINC 566A is the ARINC characteristic governing 2×5 parallel COM frequency selection — a related but distinct document from ARINC 410 covering this application. |
| G7406-04 | ARINC 429 and/or 2×5; specific variant | 118–136.992 MHz; 8.33 kHz | RTCA/DO-178B, RTCA/DO-186, ARINC 429, ARINC 566A, ARINC 716, ARINC 720, ARINC 724B, ARINC 750 | Identified by Jan SP5XZG as the control head for the Collins 618M-5 on Boeing 737-600/700/800/900 series aircraft. Digital frequency readout with ARINC 429 tuning and digital display. Certification: gableseng.com. |
| G7412 | ARINC 429 (standard on B717) | 118–136.992 MHz; 8.33 kHz | ARINC 429; smaller form factor than G7400/G7406 | Standard on Boeing 717. Dimensions 2.235″ H × 5.735″ W × 5.0″ D (shorter than G7400/G7406). Not documented as supporting 2×5 parallel mode. |
Section 8 — Summary Reference Table
Manufacturer |
Model Family |
Era |
ARINC 410 |
Serial Option |
Primary Evidence |
|---|---|---|---|---|---|
| Collins | 618M-1/2/3 series | 1960s–70s | Confirmed | None | SEA: “2-out-of-5, in accordance w/ ARINC 410” |
| Collins | VHF-20/20A/20B | Early 1970s | Confirmed | None | SEA: “2-out-of-5, in accordance w/ ARINC 410”; 313N-5A documentation |
| Collins | 618M-4/4A & 618M-5 | 1980s–1990s | Probable ARINC 429 | ARINC 429 (primary); 2×5 compatibility not confirmed | 618M-5 controlled by Gables G7406-04 on B737NG; per Jan SP5XZG. 8.33 kHz capable. |
| Late 1970s–80s | Confirmed | CSDB (RS-422A); strapping-selectable | Collins IB 523-0771858; explicit ARINC 410 pin spec | ||
| Collins | VHF-22/22A/22B/22C | 1980s–2013 | Confirmed | CSDB (RS-422A); P1-32 strapping | VHF-22C: “25-kHz only on 2-out-of-5”; IB 523-0771858 |
| King | KTR-9000 | Late 1960s | Probable | None expected | Era; manual 006-0042-00 needed |
| King | KTR-9100/9100A | Early 1970s | Probable | Unknown | Successor to KTR-9000; pre-1983 (pre-Bendix/King merger) |
| Bendix | RTA-41/41A/41B | Mid-1960s | Probable | None expected | 1965 overhaul manual; contemporary of 618M-2 |
| Bendix | RTA-42/42A | Mid-to-late 1960s | Probable | None expected | RTA-41 successor; same era and market |
References and Sources
- ARINC 410 — Mark 2 Standard Frequency Selection System. GlobalSpec Standards Database. First published 1 October 1961; revised 1 October 1965; 67 pages; status: inactive. The formal standard document whose publication date establishes the earliest date of ARINC 410 compliance for the 618M-1 series.
- ARINC 429 — Mark 33 Digital Information Transfer System (DITS). Wikipedia / multiple sources. First published July 1977; issued as ARINC 429-1 in April 1978. Data rates: 12.5 kbit/s (low speed) and 100 kbit/s (high speed). The standard that replaced ARINC 410 in new-generation aircraft.
- Collins VHF-20 documentation archive, TSC-60 avionics archive: 313N-5A feature listing, “Digital binary (2×5 wire) frequency selection as per ARINC 410.” tsc-60.cellmail.com.
- Two-out-of-five code — Wikipedia. Incorporates public domain material from Federal Standard 1037C, General Services Administration. Reference for the constant-weight error-detection property and the multiple weight-set variants of the code. The specific weight assignment used in the ARINC 410 aviation implementation is defined in the ARINC 410 standard document itself.
- Collins instruction book 523-0771858, VHF-21( ) and VHF-22( ) VHF Comm Transceiver, revised 1 October 2001. Primary source for VHF-21/22 dual-mode (ARINC 410 parallel + CSDB serial) confirmation. Contains the explicit 2-out-of-5 negative-active pin specification, serial/parallel strapping procedures, and the VHF-21 serial-mode detection explanation. Available through pdfcoffee.com archive.
- SEAEROSPACE, Collins Aerospace 618M-2B Specifications: “Frequency control: 2-out-of-5, in accordance w/ ARINC 410. Power output: 25 watts minimum. Frequency range: 118.000–135.975 MHz. Physical: ½ ATR short ARINC box; 17.3 lbs; +27.5 Vdc, 7 A max transmit.” seaerospace.com.
- SEAEROSPACE, Collins Aerospace 618M-3 Specifications: “Frequency control: 2-out-of-5, in accordance w/ ARINC 410. Power output: 25 W nominal; 20 W minimum. Frequency range: 118.000–135.975 MHz. Physical: ½ ATR short ARINC box; 11.0 lbs; +27.5 Vdc, 7 A max transmit.” seaerospace.com.
- SEAEROSPACE, Collins Aerospace VHF-20A Specifications: “Frequency control: 2-out-of-5, in accordance w/ ARINC 410. RF power output: 20 W nominal; 16 W minimum. Frequency range: 118.000–135.975 MHz. Physical: 3.750″W × 3.50″H × 13.9″L; 5.6 lbs; −65 to +131°C.” seaerospace.com.
- Fieldtech Avionics & Instruments, VHF-22C (part 822-1113-021): “25-kHz increments only when operated on 2-out-of-5 tuning” and “The transceivers accept either 2-out-of-5 parallel or RS-422A serial-digital tuning data.” ftav.com. The VHF-22 serial output active in parallel mode detail is sourced from Collins instruction book 523-0771858 (IB-5230771854), which specifies that CSDB output ports remain active regardless of the serial/parallel strapping selection.
- Rockwell Collins Product Discontinuance Bulletin 2013-107M, VHF-22 and VHF-422: VHF-4000 “does support both the ARINC 429 and CSDB tuning busses” — confirming CSDB was the VHF-22 serial bus and that ARINC 429 entered the product line with the VHF-422/4000 generation.
- BendixKing corporate history: “King Radio released the KTR 900, the first all solid state transceiver, for airlines in 1966.” bendixking.com/en/about-us/history. Primary source confirming the KTR-900 and the KTR-9000’s heritage. Flying Colors Air Parts, KTR-9000 (064-1004-00, removed 1969 LearJet 24B): operational era confirmation. flyingcolorsairparts.com. King Radio history: founded 1959 by Ed King Jr.; acquired by Allied Corporation 1983; merged with Bendix Aviation to form Bendix/King; now part of Honeywell International Inc.
- WorthPoint auction record, Bendix RTA-41A/41B overhaul manual (1965 edition, 199 pages). Production era confirmation. worthpoint.com.
- Jan SP5XZG, original research query, March 2026; follow-up observations, April 2026. Jan’s original question identified every unit in the initial compilation correctly. His follow-up raised three significant additions: (1) the 618M series continued as the 618M-4 and 618M-5 with ARINC 429 and 8.33 kHz capability; (2) the 313N control head family is substantially larger than the two entries originally documented, extending from the 313N-1 (618F-era) through numerous variants including dual COM/NAV Dzus panel units; (3) Gables Engineering G7406 series control panels support both ARINC 429 and 2×5 parallel tuning simultaneously — establishing that the dual-mode architecture appears on the control head side as well as the transceiver side. Jan has indicated a preference for limited web attribution and is identified by callsign only in this document.
- Gables Engineering, G7406 VHF COMM Control Panel product page and variant descriptions. Source confirming G7406 series supports “ARINC 429 and/or 2×5 radio tuning” and 8.33 kHz compliance. G7406-04 confirmed as control head for Collins 618M-5 on Boeing 737-600/700/800/900 per Jan SP5XZG. gableseng.com.
- SEAEROSPACE, Collins 313N-4D specifications: “Models available that contain isolation diodes to allow transferring between two control units without interaction in accordance with ARINC characteristic 410.” Source confirming ARINC 410 compliance of the 313N-4 series. seaerospace.com.
- SEAEROSPACE, Collins 313N-5 and 313N-5A specifications: “All parallel tuning control heads, including the 313N() series, CTL-20, and CTL-21 controls, are not capable of providing 8.33 kHz tuning.” Source confirming the absolute constraint on all 2×5 parallel control heads. seaerospace.com.
- TSC-60 Collins VHF-20 Documentation Archive. Source confirming 313N-2D for VHF-20 installations with ARINC 410 2×5 frequency selection; VHF-21/22 manual citation confirming 313N-() family compatibility with VHF-21/22 in parallel mode. tsc-60.cellmail.com.
- SEAEROSPACE, Collins Aerospace VHF-22C product page: “8.33 kHz channel spacing was required above FL195 in the ICAO European region as of 15 March 2007.” Reference for the 8.33 kHz regulatory mandate timeline. seaerospace.com. The initial ICAO European mandate above FL245 from 15 October 1999 is documented in ICAO Annex 10 and FAA Advisory Circular AC 90-36B. Parallel-format ARINC 410 control heads (313N-5A, CTL-20, CTL-21) cannot encode 8.33 kHz channel increments; they were therefore not usable in compliant European above-FL195 operations from 2007 onward regardless of the transceiver type installed.