Emergency Stand Alone (ESA) is a term used by the vendors of telephone equipment such as Nortel
DMS-100
The DMS-100 is a member of the Digital Multiplex System (DMS) product line of telephone exchange switches manufactured by Northern Telecom. Designed during the 1970s and released in 1979, it can control 100,000 telephone lines.
The purpose of ...
, Lucent
5ESS or GTD-5.
Typically, small towns or communities have telephone services provided from a "remote switching unit" which is controlled by the more powerful host switching complex. ESA occurs when the host/remote links are severed, thus leaving the region in “community isolation”. While in the ESA mode, the town/community is limited to only receiving or placing calls within that community/town.
Larger towns/regions may have several remote switching units which required “backdoor trunking” to connect all remote units during ESA within the same town/community. Special translations can be implemented to allow 911 to be redirected to a local number such as the local police station or fire hall that resides within that same community/town.
Multiplexing
Telephone exchange equipment
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