I remember a couple of telephone offices in southern Arkansas in the
40s and 50s. The first one was a manual office on the second floor of a building. As someone mentioned there were high ceilings - about 16 feet in this case. There were windows that could be opened, and in the switchboard room there were oscillating fans mounted on the walls. In old buildings you sometimes see fan outlets high up on the walls; you can recognize them by the large bolt they have to hold the fan. There was not much electronics in this office. Maybe 3 channels of H1 carrier with maybe 4 tubes each. Tungar rectifiers to charge the batteries. Later there was added a program amplifier for radio networking, a 48 volt power system, a few 24 volt rectifiers, and a mobile radiotelephone setup which included a 250 watt transmitter and a receiver with a bunch of tubes. Of course the transmitter was not used much, so only keeping the tubes heated generated heat.Then there was a SxS office on a one-floor building in the early
1950s. I'm trying to remember if it had A/C in the switchboard area from the beginning. Possibly in the business office too. The equipment room did not get A/C until fairly late, when a bunch of O and N carrier equipment came in.jhhaynes at earthlink dot net