The smallest Protel LTS servers are housed in a black steel case designed to be wall-mounted using the supplied key-locking bracket, or to sit on a shelf.

On the back panel of the PBX, there are two small recessed holes that you will need a paper clip or other tool to access.  With the power adapter plugged into an active AC outlet, and the adapter cable plugged into the power jack on the back panel, press the paper clip into the power recess momentarily.  There is a green LED lamp directly above the switch that will glow steady when the unit is powered up.  The power switch is marked with the universal equipment power symbol:

Standby, power button Free Icon

The other switch is to reboot the PBX.  It is marked like this:

These servers are shipped with the server BIOS settings in the default mode, which does NOT reboot the server in the event of a power failure.  This is a precaution to prevent damage to the server components in the event of a power surge.

You can change the server BIOS power management settings so that the PBX returns to its last state automatically after power is restored.  Follow the instructions HERE.