The compasses are made out of two main parts: a beam and a base. The beam has a turning point on one side and a pointy shape for drawing circles on the other. You can put the turning point, which will be the center of the circle in the base. The base, which has three strong magnets, keeps the compass in place on the TactiPad board, which has a metal layer below the drawing surface. The beam can be moved around the base clockwise and counterclockwise just above the sheet. The beam has as special ball mounting, so you can slightly tilt the beam. This makes it easier to draw a circle with the pointy shape.
Positioning the center
The base has a semi-circle shape with a diameter of almost 6 centimeters, with three little legs pointing out. It looks a bit like a round capital E. The middle leg has the shape of a triangular arrowhead of which one corner has been cut out. The arrowhead can be used to precisely place the center of a circle on a specific point in the drawing.
Adjusting the radius
The pointy shape which is used to draw the circles can slide along the beam. The beam has a measure designation per 0.5 centimeters. Using this indication you can set the radius with 0.5 centimeter increments. The smallest possible circle you can draw is 3 centimeters, whilst the largest is 12 centimeters.
Tactile center indication
The bottom end of the turning point has three very small spikes. When you press and turn the knob on top, without moving the whole beam, a small tactile circle is created. This way you can indicate the center of the circle drawn.