Multi Phone Hold
We have a number of locals that dial more than one set and, on our legacy Nortel Meridian, the users used to be able to place the call on hold on one set, and pick it up on another. When we switched to Asterisk, this was the most complained about missing feature, so I came up with the following trickery to make our Polycoms emulate the same functionality.
SLA=Shared Line Experience
SLA can also be confused with Service Level Agreement which is also a telecom acronym.