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Marine Corps MOS · Communications

0621 Transmissions System Operator

Current service use not established

This code is listed in the directory. Inclusion alone does not confirm current service use.

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Overview

A Transmissions System Operator installs, operates, and maintains single and dual channel radios, vehicular and man-pack systems, and multichannel line of sight systems across HF, VHF, UHF, and SHF bands. The operator establishes over-the-air links between distant stations, manages message traffic and information flow, and implements authorized changes to network parameters, encryption protocols, and transmission security.

Minimum clearance: Secret

Minimum ASVAB: CL 100 or EL 100

ASVAB policy: Not policy-reviewed · coverage unknown · as of 2026-10-19

Program scope has not been reviewed.

Policy applicability and coverage of the program's score routes have not been reviewed. Shown-route arithmetic is not an eligibility decision.

Source: navmc-1200-1l-fy26 (source date 2025-03). Policy applicability has not been established.

See if you would hit this score: free ASVAB practice test

Core Skills

  • Multiband, multichannel line-of-sight radio link setup
  • Field-expedient antenna integration into transmission networks
  • Authorized network parameter and encryption changes
  • Message traffic and information flow management

Civilian Career Paths

Career associations are editorial assessments of the cited evidence, not an official crosswalk unless the evidence explicitly says so. O*NET supplies civilian occupation information, not proof of a military match. Related experience does not confer civilian qualifications. Tasks and tools below describe civilian work, not military training.

Radio, Cellular, and Tower Equipment Installers and Repairers

Installing and maintaining multiband radios, establishing transmission links, and integrating field-expedient antennas transfer directly to radio equipment installation and service.

How to prepare: Complete a hands-on antenna and transmission-line installation lab that includes sweep testing and inspection of mounting, grounding, and weatherproofing. Maintaining, adjusting, or internally repairing FCC-licensed radiotelephone transmitters in aviation, maritime, and international fixed public radio services requires the General Radiotelephone Operator License.

What the civilian work involves
  • Install all necessary transmission equipment components, including antennas or antenna mounts, surge arrestors, transmission lines, connectors, or tower-mounted amplifiers (TMAs).
  • Test operation of tower transmission components, using sweep testing tools or software.
  • Inspect completed work to ensure all hardware is tight, antennas are level, hangers are properly fastened, proper support is in place, or adequate weather proofing has been installed.
Civilian tools and software (examples)
  • AERONET calculator

Telecommunications Equipment Installers and Repairers, Except Line Installers

Communications equipment installation, maintenance, and network integration provide a foundation for installing and testing civilian telecommunications systems.

How to prepare: Complete a practical telecommunications lab that uses circuit diagrams and test meters to isolate faults and verify repaired equipment.

What the civilian work involves
  • Test circuits and components of malfunctioning telecommunications equipment to isolate sources of malfunctions, using test meters, circuit diagrams, polarity probes, and other hand tools.
  • Test repaired, newly installed, or updated equipment to ensure that it functions properly and conforms to specifications, using test equipment and observation.
  • Assemble and install communication equipment such as data and telephone communication lines, wiring, switching equipment, wiring frames, power apparatus, computer systems, and networks.
Civilian tools and software (examples)
  • Cisco IOS

Broadcast Technicians

Radio operation, transmission-link establishment, and equipment maintenance provide transferable experience for broadcast transmitter monitoring and service.

How to prepare: Practice recording transmitter readings and adjusting signal quality in a supervised broadcast equipment lab.

What the civilian work involves
  • Monitor and log transmitter readings.
  • Monitor strength, clarity, and reliability of incoming and outgoing signals, and adjust equipment as necessary to maintain quality broadcasts.
  • Report equipment problems, ensure that repairs are made, and make emergency repairs to equipment when necessary and possible.
Civilian tools and software (examples)
  • Microsoft Excel

Training & Development

Choose credentials for your target role. COOL funding markers describe program listings, not a guarantee of eligibility or funding.

Getting Started

  • Associate Electronics Technician (CETa)

    Strengthen electronics theory, circuit testing, and telecommunications fundamentals for equipment installation and maintenance.

    For: Radio, Cellular, and Tower Equipment Installers and Repairers, Telecommunications Equipment Installers and Repairers, Except Line Installers, Broadcast Technicians

  • General Radiotelephone Operator License (PG)

    Support specialization in regulated radiotelephone transmitter maintenance, including aviation and maritime equipment.

    Eligibility and preparation: Satisfactory knowledge of FCC rules, ability to send and receive spoken messages correctly in English, and passage of written Elements 1 and 3 or applicable examination credit.

    For: Radio, Cellular, and Tower Equipment Installers and Repairers

Notes & Sources

Evidence for this guidance (8 documents)
  1. NAVMC 1200.1L (FY26, in force): MOS 0621

    [1] MOS 0621 section "a. Summary"; cached text line 30001; NAVMC 1200.1L signed 2025-03-07, in force until 2026-10-01

    Supports: Multiband, multichannel line-of-sight radio link setup, Field-expedient antenna integration into transmission networks, Authorized network parameter and encryption changes, Message traffic and information flow management, Radio, Cellular, and Tower Equipment Installers and Repairers (O*NET 49-2021.00), Telecommunications Equipment Installers and Repairers, Except Line Installers (O*NET 49-2022.00), Broadcast Technicians (O*NET 27-4012.00)

  2. O*NET: Radio, Cellular, and Tower Equipment Installers and Repairers

    [2] O*NET 30.3 occupational data

    Supports: Radio, Cellular, and Tower Equipment Installers and Repairers (O*NET 49-2021.00)

  3. COOL credential mapping: General Radiotelephone Operator License (PG)

    [3] 0621 cached COOL credential feed

    Supports: Radio, Cellular, and Tower Equipment Installers and Repairers (O*NET 49-2021.00), General Radiotelephone Operator License (PG)

  4. O*NET: Telecommunications Equipment Installers and Repairers, Except Line Installers

    [4] O*NET 30.3 occupational data

    Supports: Telecommunications Equipment Installers and Repairers, Except Line Installers (O*NET 49-2022.00)

  5. O*NET: Broadcast Technicians

    [5] O*NET 30.3 occupational data

    Supports: Broadcast Technicians (O*NET 27-4012.00)

  6. COOL credential mapping: Associate Electronics Technician (CETa)

    [6] 0621 cached COOL credential feed

    Supports: Associate Electronics Technician (CETa)

    [7]ETA International: Associate Certified Electronics Technician · CETa description and CETa Exam Info; retrieved 2026-09-23

    Supports: Associate Electronics Technician (CETa)

  7. eCFR: 47 CFR 13.201 - Qualifying for a commercial operator license or endorsement (FCC)

    [8] sec. 13.201(a) and (b)(2); eCFR current through issue date 2026-09-21, text retrieved 2026-09-23 via eCFR API

    Supports: General Radiotelephone Operator License (PG)

  8. eCFR: 47 CFR 13.203 - Examination elements (FCC commercial radio operators)

    [9] sec. 13.203(a)(1)-(2); eCFR current through 2026-09-21, retrieved 2026-09-23 via eCFR API

    Supports: General Radiotelephone Operator License (PG)

Defense contractor jobs for 0621

Predecessor codes

Historical codes with documented links to 0621. Each history page explains the change.

2821Technical Controller (PMOS)

Descriptions may be summarized for clarity. Verify all information with your branch career counselor or official military documentation before making career decisions.

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