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It could be a phone system in some cases.

Nortel/Avaya BCM 4.0 and BCM50/450 R1 and above has/had this option built in and unlocked via keycode called "Advanced Paging Productivity Package"

This allows you:
-to schedule pre-recorded announcements from the same place you record Auto Attendant greetings.
-program a F9XX code to instantly page a specified greeting, the code can be applied to a button on the set or add an assistance 1202 Call Button on the wall/pillar.
-send a specific text message to another set.

I use mine in my office/home for Grandfather Chimes on the hour and baseball game reminders etc.