For decades, many businesses have had public address systems integrated with their telephone network. An extension could dial a special code and then be connected to the P.A. This was often used, among other functions, to page managers. (This capability existed long before Divesture, and apparently a rare example of where Bell allowed an interface between its equipment and privately owned customer equipment).
A modern adaption is supermarket managers carrying cordless telephone sets allowing them to receive or make calls while on the store floor, including P.A. announcements.
Recently, an unknown person used a Walmart store telephone to access the P.A. system to broadcast offensive comments throughout the store. Police and store officials are investigating.
Walmart announced its changing its system to restrict access.
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