rating insignia; the enlistment requirements (e.g. submarine ratings are volunteer duty), initial 'A' school training, specialized 'C' school training, job assignments (billets), specific qualification, and community managers are unique to each of the four service rating. This prevents someone trained in any of the four service rating from easily transferring to another of the four service rating without first going through significant retraining and qualification that would be required by anyone transferring from any of the other general rating in the Navy. There is prior usage to ETN and ETR. At least through the 1970s, the "N" represented a Communications ET while the "R" represented a Radar ET. This was usually determined by the ET "A" School curriculum taken by the student in later phases of training. The "N" or "R" designation only applied to 3rd or 2nd class petty officers (paygrades E4 and E5). 1st class and chief petty officers (paygrades E6 through E9) did not have a "N" or "R" designation. Elimination of all naval ratings On 29 September 2016, the Navy moved away from traditional ratings to an alphanumeric system of Navy Occupational Specialty (NOS) codes. The ET-related NOS codes were: for ET, B420; for ETR, C126; for ETV, C121; for ETN, D110, D111, or D112. On 21 December 2016, however, after months of widespread complaints, Chief of Naval Operations John Richardson released a message announcing a restoration of all U.S. Navy Ratings. Electronics technician service ratings Electronics technician (ET) General description ETs are responsible for electronic equipment used to send and receive messages, computer information systems, long range radar, and calibration of test equipment. They maintain, repair, calibrate, tune, and adjust electronic equipment used for communications, detection and tracking, recognition and identification, navigation. Working environment Jobs performed by ETs are performed throughout the Navy's fleet of surface ships including aircraft carriers and Aegis cruisers and destroyers, and at communication activities and repair activities ashore. Minimum requirements ASVAB: MK + EI + GS = 156 + AR = 223 Must have normal color perception Must have normal hearing Security clearance required Must be a U.S. Citizen Employment and subspecialties Entry rates ET3-ET2 (E4-E5) specialize as electronics communications technician, electronics data systems technician, or electronics radar systems technician. ET1-ETC (E6-E7) are electronics systems managers. Electronics Communications Technicians Maintain shore-based, ship-based, portable communications equipment, and portable Mechatronic equipment, including all associated cabling, computer, multiplexing, motor, switching, cryptographic, recording, cooling