What is an ELT?
Well, I think you can tell from the responses, ELT's are generally kept way from the rest of the crew, that is why they have their own little lab and sometimes we put the lock on the outside.
What is the difference between an ET and and EM?
The other difference between ET and EM is the watches they qualify for. EM's generally qualify as Electrical Plant Operator (EO) where as ET's qualify as Reactor Operators (RO). So ET are cross trained in electronics and reactors, where the EM mainly stick to electrical.
Also, ET's have to qualify as EO, to be Shutdown Maneuvering Area Watch (SMAW) qualified. When the reactor is at power, there is an Engineering Officer of the Watch (EOOW) in the Maneuvering Room with an EO and RO on watch. When the reactor is shutdown, there isn't an EOOW in Maneuvering and the SMAW is in charge of the maintaining the reactor and electrical systems. Although some EM's do qualify as SMAW, most SMAW's are ET's, since they are qualified reactor operators. Only had 2 EM qualified SMAW when I was in.