Level with electrically responsive instrument

Claim 1

A LEVEL COMPRISING THE COMBINATION WITH A GRAVITATIONAL INDICATOR COMPRISING AN ELONGATED VIAL CONTAINING LIQUID AND AN ELONGATED BUBBLE MOVABLE IN THE VIAL ALONG A PREDETERMINED PATH, OF A LIGHT SOURCE ELONGATED IN GENERAL PARALLELISM WITH THE VIAL, A SERIES OF PHOTO SENSITIVE RECEPTORS COMPRISING STRIPS OF SEMI-CONDUCTOR MATERIAL AND EXTENDING ALONG SAID PATH AT ONE SIDE OF THE VIAL AND OPPOSITE SAID LIGHT SOURCE, SAID STRIPS BEING ELONGATED ALONG SAID PATH, THE VIAL BEING OFFSET LATERALLY FROM A PLANE INCLUDING THE LIGHT SOURCE AND THE CENTER LINE OF SAID STRIPS, WHEREBY TO LOCATE A MENISCUS AT THE SIDE OF SAID BUBBLE BETWEEN THE LIGHT SOURCE AND A GIVEN STRIP AREA WITH WHICH SAID BUBBLE REGISTERS, AND THEREBY REFRACTS LIGHT FROM SAID SOURCE AND PROGRESSIVELY VARIES IN ACCORDANCE WITH BUBBLE MOVEMENT THE AMOUNT OF LIGHT REACHING SAID GIVEN STRIP AREA FROM SAID SOURCE.