Abstract: A proximity instant-on switch for medical and dental instruments that includes a magnetically-responsive switch incorporated into the handle of the instrument and a permanent magnet embedded into the instrument cradle at a position adjacent the location of the switch when the instrument is placed in the cradle. The presence of the magnetic field created by the magnet maintains the switch in its open state while the instrument is in place in the cradle. However, upon removal of the instrument from the cradle, the loss of the magnetic field closes the switch thereby automatically energizing the instrument.

Abstract: A switching control circuit for an electrically adjustable patient chair that utilizes a relay control circuit comprised of a plurality of switching control relays connected in a binary switching arrangement which in the preferred embodiment herein, permits the use of only three control relays to control six motor adjustment functions.

Abstract: A control circuit for an electrically adjustable patient chair that is adapted when actuated by the momentary depression of a start button, to automatically return the chair to its fully down and tilt forward position. The control circuit includes a multiple-pole relay that is latched in the closed position to energize both motor windings by a solid state switching device that is gated to the on state by a current transformer that senses the load current in a conductor that passes through the core of the transformer. The adjustment motors remain energized until a pair of limit switches are opened upon the chair attaining its exit position. The resulting current drop to zero in the load line is sensed by the current transformer which turns off the solid state switching device which in turn unlatches the relay.