skill in the art the reference voltages v 1 through v 4 are adjustable by means of potentiometers 83 85 87 and 81 respectively calibration of the comparators may be most easily accomplished by connecting resistors of the selected threshold values desired between lead 32 and 71 and operating test button 90 the appropriate potentiometer 83 85 or 87 is then adjusted to just obtain a high output from the associated comparator as may be noted comparator 78 utilizes an opto iosolator 82 to operate relay 79 push buttons 90 92 may be used for manual testing of motor 50 and 60 when neither motor is running power supply 10 utilizes a conventional low voltage transformer 11 a bridge rectifier 12 and a voltage regulator 14 to produce 12 volts regulated power to the switching and comparator circuits power supply 10 also supplies power to high voltage supply 20 which is preferably an oscillator type having oscillator transformer 21 with a high voltage secondary feeding a voltage doubler rectifier circuit generally this type of high voltage circuit is desired for safety purposes since any attempt to draw excessive current from the supply will produce loading and cessation of oscillation it is anticipated that the leakage resistance monitoring system of the invention can be mounted integral with motor control panels such as.