A theatre paging system is a system of linked speakers, controllers, outstations and amplifiers which allow Front of House staff, the Stage Manager/Deputy Stage Manager and the building management to make PA (public address) announcement. These announcements are typically used to welcome the audience and alert them to the opening of the show or the starting of the second half. In rare cases the paging system can also be used to alert persons in the building to emergencies, fire alarm tests and power cuts.
A paging system will typically have several 'zones' or areas that can be individually & separately paged by the user from the outstation (the control point they are using). For example, there might be a Backstage zone to page the dressing rooms and green rooms, a FOH zone to page the box office and bar areas, and an Emergency zone to page the entire building: backstage, front of house, the auditorium itself and outside areas in the yard/street.
The ADC Theatre has a strict code of conduct for paging announcement that you will be taught if you train as a SM or DSM. This is taken quite seriously and wilful flagrant abuse will likely result in the individual being sanctioned be Theatre Management and, in severe circumstances, the case being referred to the individual's college tutor.