S1 Pro Pole Cup Switch
The S1 Pro uses an accelerometer to determine if it is in the tilt-back, horizontal or vertical position. It also has a switch inside the pole cup to determine if it is mounted on a speaker stand. Based on the orientation and the switch, the S1 Pro automatically applies the correct EQ. If you depress the switch the speaker stand EQ is applied regardless of the orientation of the S1 Pro.
Here's a picture of the switch inside the pole cup.
Warning - Do NOT use Speaker Stands Like This
Bose recommends using speaker stands that have solid, smooth surfaces. Do not use stands like the one shown below. It will damage the switch in the pole cup.
Warning - Do NOT use speaker pole adapters
Bose recommends that you do NOT use speaker stand adapters like the Hercules SS100B. You could damage switch in the pole cup.