A facility's KSU or PBX can integrate with the T3-SC to provide communications between telephone instruments and intercom stations and consoles. Administrative staff outside secure areas can access the intercom and paging capabilities of the T3-SC system.
For a phone user, answering an intercom call-in is no different than answering a regular call. An intercom call is treated as any other type of call, and therefore can be involved in regular phone feature functioning, such as being put on hold or transferred.
Telephones that are part of the public telephone network, outside of the KSU/PBX, can access the T3-SC system. This, of course, includes mobile phones on a cellular network.
Access to the T3-SC system from outside lines is protected by security codes to prevent unauthorized use.