Gembird’s SilverShild PMs are USB-controlled power-outlets. They can be controlled with help of sispmctl. As stated on the projects homepage:

SIS-PM Control for Linux aka sispmctl is an application enabling the use of the GEMBIRD (m)SiS-PM device family under Linux.

On my system, sispmctl resides in /usr/local/bin/. Here are some simple commands:

Show devices

$ sispmctl -s

Example output, used in the following commands:

Gembird #0
USB information:  bus 002, device 028
device type:      4-socket SiS-PM
serial number:    01:01:3e:1f:00

Switching sockets

Toggle all sockets:

$ sispmctl -D 01:01:3e:1f:00 -t all

Switch socket 1 off:

$ sispmctl -D 01:01:3e:1f:00 -f 1

Switch socket 2 on:

$ sispmctl -D 01:01:3e:1f:00 -o 2