The ShoreTel 24A is an analog extensions voice switch that supports a total of 24 extensions. The SG-24A is a standard 1U sized switch and features two LAN ports, one patch panel port, one power fail port, a DB-9 serial port, and two stereo jacks. The stereo jacks are 3.5mm, the first is used for on-hold background music while the second is used for a paging system.