Abstract: A probe including means for indicating when the probe has come into physical contact with a target. The probe has a deformable opaque tip containing a transparent window which is normally covered by a shutter. When the probe contacts a target the probe tip deforms, moving the window away from the shutter. Light will be reflected from the target through the window to indicate that contact has been made.

Abstract: In a random access storage device a head transported relative to a rotating assembly of flexible disks and a pair of co-rotating end plates operates in clearance spaces formed by sliding the disks apart at a selected interface. One of the end plates is attached to a low friction spline which is quickly shiftable between predetermined axial limit positions. In the most confining position of this plate a single selected interface space between the disks is partially opened by deflection of the disks. The partial opening is sufficient to establish a pressure difference relative to the other interfaces but not enough for unobstructed entrance of the head. Shortly after formation of the partial opening the shiftable plate is actuated away from the disks in a quick movement.