voltage at the respective third comparator output pin 104 2104 3104 4104 5104 6104 the respective fourth comparator positive input pin 68 2068 3068 4068 5068 6068 is connected to the 5v reference voltage and the respective fourth comparator negative input pin 66 2066 3066 4066 5066 6066 is connected to the 15 volts present at the respective signal voltage trace establishing a reverse bias in the respective fourth comparator and the respective fourth comparator outputs a low state voltage at the respective fourth comparator output pin 124 2124 3124 4124 5124 6124 the respective green led inverting driver input pin 86 2086 3086 4086 5086 6086 receives a high state voltage from the respective first comparator output pin 82 2082 3082 4082 5082 6082 and a low state voltage from the respective second comparator output pin 84 2084 3084 4084 5084 6084 the low state voltage from the respective second comparator output pin pulls the high state output of the respective first comparator pin to a low state and the respective green led inverting driver outputs a high state voltage at the respective green led inverting driver output pin 92 2092 3092 4092 5092 6092 not allowing current to flow through the respective green led 74 2074 3074 4074 5074 6074 and not illuminating the respective green led the respective yellow led inverting driver input pin 106 2106 3106 4106 5106 6106 receives a high state voltage from the respective third comparator output pin 104 2104 3104 4104 5104 6104 and the respective yellow led inverting driver 100 2100 3100 4100 5100 6100 outputs a low state voltage at the respective yellow led inverting driver output pin 112 2112 3112 4112 5112 6112 allowing current to flow through the respective yellow led 96 2096 3096 4096 5096 6096.