Anyone interested in intercoms or speakers in schools/buildings?

I remember my elementary school had rectangular speakers in the rooms, and on the left side were the clocks. I forget what brand they were. There were call buttons in all the rooms too. I saw the big main unit behind the front desk, it had the microphone on top and there was also a receiver that looked like a car stereo and had a cassette player. Two funny instances happened with that system. Once one afternoon someone played the radio over it somehow for about 30 seconds, then it stopped. Another time we were having a fall event at school (I don't even remember what) but they were playing this cheezy music about slicing up the pumpkins or something over the intercom.

In middle school the system looked much the same, but a little older possibly. (My middle school was built in 1979, but one or two classroom wings were from the 1940s.) The only story about that one was that kids would press the call button when the teacher stepped out of the room, and the lady at the front desk would respond to the call but no one would said anything. When she heard the snickers she got mad.

Then in high school, the original parts of the school had a square speaker on the wall that was silver and a silver framed clock next to it. The clocks here I remember said "DuKane" on them. That was in the original buildings that were built in 1971. The newer parts of the school from 2000 had square black speakers that said BOGEN on them and the call buttons. The clocks in those buildings were just regular plastic battery clocks like you could get at Walmart. I suspect the DuKane clocks were battery powered as well, because I seem to remember one stopped working and they just put new batteries in it. I am almost certain the ones in elementary school though, were interconnected because sometimes the time would be wrong and then they would suddenly move fast and reset.

Also, all of the bells in those schools weren't really a ringing bell but the intercom would play a beeeeppp! for the early/tardy bell.

We have an intercom system here for gaining entry into the building. A visitor can press the button for our flat and once we have spoken to them we can let them in by pressing a button to release the door latch, or tell them to go on their way...