14.6. Shared Line Appearances

In Asterisk, Shared Line Appearances (SLA)—sometimes also referred to in the industry as Bridged Line Appearances (BLA)—can be used. This functionality can be used to satisfy two primary use cases, which include emulating a simple key system and creating shared extensions on a PBX.

Building key system emulation is the use case for which these applications were primarily designed. In this environment, you have some small number of trunks coming into the PBX, such as analog phone lines, and each phone has a dedicated button for calls on that trunk. You may refer to these trunks as line 1, line 2, and line 3, for example.