The Radio Corporation of America (RCA) was founded in 1919 as a wholly owned subsidiary of General Electric (GE) and was spun off into its own company in 1932. They made radio receivers, then television sets, then started the NBC television network.
What does this have to do with microwaves? From our message board (from Timothy Boles)
They were certainly a semiconductor pioneer in the development of discrete microwave small signal, low noise, CATV, and high power devices and multi-chip modules throughout the 1960's and through 1975 (when they exited all future development projects though they continued manufacturing of certain parts beyond the 1975 timeframe). Various engineers left to start companies like MSC (already listed in your encyclopedia).
In addition, RCA also was prominent in the development and sale of various substems and systems thoughout the 50's, 60's, & 70's; i.e. RCA Moorestown at one tome was 2nd or 3rd in mobile radio behind Motorola. All this radically changed when GE acquired RCA in its entireity in the 70's.
Need more details? Check out RCA on Wikipedia.