Adjustable boom angle warning device

Claim 1

A WARNING INDICATOR FOR INDICATING UNSAFE ANGULAR POSITIONS OF THE BOOM OF A CRANE WITH RESPECT TO THE HORIZONTAL OR THE VERTICAL, COMPRISING: A BOOM MOUNTED ENCLOSURE, TWO MERCURY SWITCHES MOUNTED IN SAID ENCLOSURE, ONE OF SAID SWITCHES BEING ROTATABLE ABOUT AN AXIS OF ROTATION, SUCH AXIS OF ROTATION BEING PARALLEL TO THE PIVOT AXIS OF SAID BOOM, THE LONGITUDINAL AXIS OF SAID SWITCH BEING POSITIONED IN THE PLANE OF ROTATION, THE OTHER OF SAID SWITCHES BEING SIMILARLY ROTATABLE ABOUT A SIMILAR AXIS OF ROTATION AND BEING SIMILARLY POSITIONED, ONE OF SAID SWITCHES BEING ROTATED TO SUCH AN ORIENTATION AS TO BE "ON" WHEN THE BOOM IS SO ANGULARLY DISPOSED AS TO BE AT OR BELOW A FIRST SELECTED ANGLE WITH RESPECT TO THE HORIZONTAL AND TO BE "OFF" WHEN THE BOOM IS ABOVE SAID FIRST SELECTED ANGLE, THE OTHER OF SAID SWITCHES BEING ROTATED TO SUCH AN ORIENTATION AS TO BE "ON" WHEN THE BOOM IS SO ANGULARLY DISPOSED AS TO BE AT OR ABOVE A SECOND SELECTED ANGLE WITH RESPECT TO THE HORIZONTAL AND TO BE "OFF" WHEN THE BOOM IS BELOW SAID SECOND SELECTED ANGLE, TWO SELECTOR KNOBS, SAID SELECTOR KNOBS BEING ROTATABLY MOUNTED ON SAID ENCLOSURE AND EACH HAVING SUITABLE INSCRIPTIONS FOR INDICATING ITS FUNCTION AND ANGULAR POSITION, ONE OF SAID SELECTOR KNOBS CONTROLLING THE ROTATION OF ONE OF SAID SWITCHES AND SELECTING THE ORIENTATION THEREOF, THE OTHER OF SAID SELECTOR KNOBS CONTROLLING THE ROTATION OF THE OUTER OF SAID SWITCHES AND SELECTING THE ORIENTATION THEREOF, A CAB MOUNTED CONTROL BOX,