In the 1950s electronics continued with the implementation of
> microwave systems. Likewise, did amplifiers require air conditioning
> in those buildings?
As I recall the first viable commercial air conditioner was installed in a department store in Detroit in 1924. A/C become common in metro movie houses in the 1930s.
It is reasonable to presume that the Bell System used it, where necessary, by the mid to late 1930s.
[TELECOM Digest Editor's Note: Trouble was, Bell's definition of 'necessary' was not like that of many people. If you went past a central office in the 1950's on a summer night when it was about to rain (but had not yet started raining) you'd see those big windows open everywhere; here and there, an operator went over and stuck her hand out the window feeling for drops of rain so the windows could be closed. As soon as the rain started, the windows went shut, the very instant it stopped raining someone went around and opened all the windows again. PAT]