This is the group I was involved with in the US Navy. I went to CTT school in 1962. This is copied from another CT veteran.
The Birth of the Communications Technician Rating
In 1948 the majority of the wartime Specialist ratings were disestablished. At that time the Communications Technician Rating (CT) was established; the Specialist Q ratings CR, TE, and IN were incorporated into the CT rating. Four CT career fields were identified as branches:
• A – Administrative
• O – Communications
• M – Maintenance
• R – Collection
Although the CT rating comprised four distinctly different branches, the service member’s branch was not a part of the rating designator.
📷Note: CAPT Holtwick, after serving as commanding officer of USS Platte (AO 24) was assigned to Headquarters, Naval Security Group as head of the Personnel and Administrative Department. In that position CAPT Holtwick is credited with establishing the Communications Technician (CT) rating in the Navy with it various branches for enlisted personnel.
In the 1956/1957 time frame, the CT rating was further sanitized when all the “General Service” ratings still serving in the Communications Intelligence field (Radioman, Teleman etc.) were converted to CT.
In 1960 two additional career fields were added to the CT rating: the Technical Branch (T) for non-morse operations and the Interpretive Branch (I) to identify linguists. Prior to 1960 the duties assigned to the T and I branch personnel had been assigned to various other branches.
Effective 1 May 1970 the CT rating was further refined when the addition of the “branch” to the CT rating designator. The third letter rating designator was added to better identify and manage each branch.
26 March 1976 BuPers Notice 1220 announced the change in title for the Communications Technician rating to the below six Cryptologic Technician ratings. The purpose of this action was to bring the designation of the Communications Technician (CT) into consonance with the Warrant Officer (744X), Restricted Line (161X) and the Limited Duty Officer (644X) Cryptologic communities.
• CTA –Administrative Branch
• CTI – Interpretive Branch
• CTM – Maintenance Branch
• CTO – Communication Branch
• CTR – Collection Branch (MM)
• CTT – Technical Branch (SpecSigs, Classic Wizard, OPELINT, TechELINT)
1991 – CTR assumed Special Signals and Morse code
📷01 Oct 2003 – EW rating converted to CTT rating.