This device converts an Alt-Azimuth style mount for use in equatorial mode. It's not exactly the same as a true equatorial mount, but for most purposes the capabilty is equivalent.

You can see in the image the tilt between the bottom plate that attaches to the mount's tripod, and the top plate that holds the mount itself. What the tilt does is reposition the mount in such a way that the axis that normally moves left and right now moves in the celestial Right Ascension (RA) coordinate, and the up / down axis now moves in the celestial Declination (Dec) coordinate.

In order to make this work correctly, the angle of tilt has to match the latitude of the location where the mount is in use. The polar alignment requirements for this set up are then essentially the same as for a true equatorial mount, i.e. the axis of rotation in RA is adjusted to make it parallel with the Earth's axis of rotation. The adjustment bolts seen at the bottom left of the image enable East / West adjustment to ensure the axis points to the true North, and another adjustment not visible in the image is for moving the angle of tilt to match the latitude of the location. When both of these adjustments are made correctly, the rotational axis of the mount points exactly at the celestial North Pole (or South Pole for use in the Southern Hemisphere).

To learn more about this device, please visit the Celestron website.