The intercom system at my building is "single user". Only the apartment for the last-pressed buzzer can unlock the door, or activate the microphone. If I do t

The intercom system at my building is "single user". Only the apartment for the last-pressed buzzer can unlock the door, or activate the microphone. If I do the latter, the person outside is stuck talking to me until I disconnect, or it times out — about a minute, I think. It doesn't happen very often, but I've left people stuck outside when they've intentionally wasted my time. The best was a couple of Jehova's Witnesses who dragged me out of the shower with their call, then proceeded to grumble that I was wasting their time as they realized they couldn't buzz anyone else. Sometimes delivery people try the all-buttons thing, but the screen on my intercom unit switches off as soon as they press the next button.