Power dividers and directional couplers might be wise to extend to fibre-optic devices if going for FA. Hard to argue against as the article now covers waveguide and fibre is a form of waveguide. Now also a comment on the talk page about integrated photonics.
The opening of Morse code history section has a couple of problems. There is a false comparison between Morse beginning development and Cook and Wheatstone putting into service. Cook and Wheatstone were in fact first. Also, much of the Cook and Wheatstone part is a bit of a diversion from the article subject
system equivalence needs a makeover, and analogical models (also in need of a makeover) should either be clearly differentiated in scope or else the two should be merged. Some material from mechanical-electrical analogies could usefully be transferred. Also, the redlinks effort variable and flow variable should link to somewhere useful. Actually, flow variable is not a redlink, but even worse, it goes somewhere irrelevant to analogies.
admittance needs the ungenarization reversed, or else individual articles created
short circuit and open circuit. We really should have a network analysis description of this. Create redirect from short circuit (circuit theory) and open circuit (circuit theory) (or appropriate the current disambiguation page at open circuit)
microwave component, redlink with one incoming link. Could do as list of microwave components
The Evolution of Character Codes, 1874-1968. List/comparison of telegraph codes? There is also a long discussion of commercial telegraph word codes in The Victorian Internet. Maybe just /Telegraph codes and incorporate a list in it.