What subjects do the call letters cover?
Subclass T Technology (General).
Subclass TA Engineering (General). Civil engineering.
Subclass TC Hydraulic engineering. Ocean engineering.
Subclass TD Environmental technology. Sanitary engineering.
Subclass TE Highway engineering. Roads and pavements.
Subclass TF Railroad engineering and operation.
Subclass TG Bridge engineering.
Subclass TH Building construction.
Subclass TJ Mechanical engineering and machinery.
Subclass TK Electrical engineering. Electronics. Nuclear engineering.
Subclass TL Motor vehicles. Aeronautics. Astronautics.
Subclass TN Mining engineering. Metallurgy.
Subclass TP Chemical technology.
Subclass TR Photography.
Subclass TS Manufactures.
Subclass TT Handicrafts. Arts and crafts.
Subclass TX Home economics.