Emergency Stand Alone - ESA

Definition of Emergency Stand Alone/ Emergency Standalone, or ESA: defines the capability of an area or region within a voice network to be self sustaining.  Having emergency stand alone capability means that a service area can continue to operate and complete all calls originating and terminating within that service area even if the connection to the broader public switched telephone network has been severed.  Intra-community voice switching capability and routing of local 911 calls are the key features of emergency standalone service. 

Historically, ESA service has been provided by a central office host switch or a subtended remote switch unit (RSU).  If the connection between the central office host switch and the broader public switched telephone network was lost then the central office host switch would continue to complete all local calls and route all 911 calls to the local public service answering point (PSAP).  Similarly, if the connection between the remote switch unit and the central office host switch was severed then the RSU would continue to complete all local calls within its service area and generally route all 911 calls to a pre-designated emergency responder, such as the local fire or police department.  Access concentration devices such as Digital Loop Carriers (DLCs) or the newer generation of Broadband Loop Carriers (BLCs) traditionally did not have any switching capability and thus no emergency stand alone service.

Aztek Networks has recently launched a new network element that brings ESA switching capability to DLCs and BLCs.  The Aztek Networks 5000S ESA switch integrates seamlessly with new or existing DLC/BLC installations and provides ESA capability to allow intra-community dialing and routing of 911 calls to pre-designated lines if the connection between the central office host switchand the concentrator is severed.