Before 911, buildings most likely had desk mounted CPV-90 systems in both lobbies, since the CPV-90 didn’t come out until 1980/1981 or so. And before Pyrotronics came out with voice systems for the World Trade center, the towers most likely had system 3 - (etc analog systems). Since the system 3 did not come out until 1970/71 or so, since the buildings were just being finished then in the early 70s. Buildings most likely used mechanical horns provided by wheelock as seen in the safety video.