These airspeeds have unrestrained movements, and their pointers rest at the twelve o’clock position. They are ram air actuated and are internally temperature compensated.
These restrained airspeeds limit pointer movement to a specific range. Their pointers rest at the twelve o’clock position and are not adjustable. They are actuated by ram air and are temperature compensated.
These true airspeeds are ram air actuated and can be adjusted to correct for changes in altitude at the turn of a knob. Their pointers rest at the 12 o’clock position and indicate true airspeed on moveable scales.