Before revision: Some texts classify wavemeters as transmission wavemeters, which have an input and an output port and are inserted into the signal path, and absorption wavemeters which are loosely coupled to the radio frequency source and absorb energy from it.
After revision: Some texts classify wavemeters as transmission wavemeters, which have an input or an output port and are inserted into the signal path, and absorption wavemeters which are loosely coupled to the radio frequency source and absorb energy from it.