SLA not only helps users share SIP trunks and FXO trunks, but also helps monitor the status of the shared lines. SLA feature works with BLF key on IP phones. For example, when an incoming call is received, all the SLA stations are informed of it and may join it if the shared line allows to barge in. When an outgoing call is made by one SLA station, all members shared with the same line are informed about the call, and will be blocked from this line appearance until the line goes back to idle or the call is put on hold.
SLA helps businesses to allocate external line resources in a more effective way. For example, you are a member of a SLA station that shares one line, you need to make an outgoing call but learn from the BLF key LED on your IP phone that the shared line is occupied. Then you can hold back from vain efforts and use the line as fast as it turns green.