The United States Coast Guard's ratings are general occupations that consist of specific skills and abilities. Each rating has its own specialty badge, which is typically worn on the left sleeve of their service dress uniform by all enlisted personnel in that particular field. On Operational Dress Uniforms, they wear generic rate designators that exclude the rating symbol. Commissioned Officers do not have ratings.
Ratings should not be confused with "rates", which describe the Navy's and Coast Guard's enlisted pay-grades. Enlisted Navy and Coast Guardsmen are referred to by their rating and rate. For example, if someone's rate is Petty Officer 2nd Class and his rating is Boatswain's Mate; when combined, Boatswain's Mate 2nd Class (BM2) defines both. Although rates E-7 above are abbreviated similar to E-4 to E-6, the combined rating is listed before rate when completely spelled out. For instance, Master Chief Electronics Technician is abbreiviated as ETCM. More examples are listed in the table below.
Reference: http://www.uscg.mil/band/careers.asp
Note: Electrician's Mates don't work on avionics. It's all shipboard maintenance and residential electrical work. [1]
Note: Electronics Technicians can work for the operations, engineering, or combat systems department, depending on the type of cutter. They also do the jobs that were once done by the Fire Control Technicians, including maintaining and operating the fire control radars, and firing the major weapons systems on the boat including the 57 MM cannon and the CIWS anti-ship missile defense system.