Adjustable electrical instruments

Claim 1

A VARIABLE RESISTOR OF THE CLASS DESCRIBED COMPRISING MEANS DEFINING A CAVITY HAVING AN AXIS, SAID CAVITY BEING OF UNIFORM NON-ROUND CROSS-SECTIONAL CONFIGURATION THROUGHOUT ITS LENGTH, A WIRE WOUND RESISTANCE ELEMENT POSITIONED WITHIN THE INTERIOR OF SAID CAVITY SO AS TO EXTEND AROUND SAID CAVITY, CONTACT MEANS OF NON-ROUND CONFIGURATION SUBSTANTIALLY IDENTICAL TO THE CROSS-SECTIONAL CONFIGURATION OF SAID CAVITY AND ENGAGING SUBSTANTIALLY ALL PARTS OF SAID RESISTANCE ELEMENT WITHIN SAID CAVITY IN A PLANE PERPENDICULAR TO THE AXIS OF SAID CAVITY, SAID CONTACT MEANS BEING CARRIED BY A CONTACT SUPPORT, AND A THREADED SHAFT EXTENDING THROUGH SAID CAVITY AND OPERATIVELY ENGAGING SAID CONTACT SUPPORT SO AS TO CAUSE MOVEMENT OF SAID CONTACT SUPPORT LENGTHWISE OF SAID CAVITY AS SAID THREADED SHAFT IS TURNED, SAID CONTACT SUPPORT BEING PREVENTED FROM ROTATING WITH SAID SHAFT BY THE SLIDING ENGAGEMENT OF SAID NON-ROUND CONTACT MEANS ON THE RESISTANCE WIRE POSITIONED ON THE INNER SURFACE OF SAID NON-ROUND CAVITY.