| 摘要 |
<p>LEVEL SELECTIVE A-C MONITORING CIRCUIT A circuit for monitoring an a-c input signal comprising a selectable gain amplifier responsive to the input signal, an a-c to d-c converter for converting signals at the output of the selectable gain amplifier to corresponding d-c values, a first comparator for comparing said d-c values to a predetermined minimum d-c value, a second comparator for comparing the d-c values to a predetermined maximum d-c value, the predetermined maximum value corresponding to a maximum acceptable value of the input signal, a third comparator for comparing said d-c values to a predetermined absolute maximum a-c value, and feedback means connected between the output of the first comparator and the third comparator for causing the third comparator to compare the d-c values to said minimum d-c value, the predetermined absolute maximum value corresponding to an absolute maximum acceptable value of the input signal, the absolute maximum acceptable value being greater than the maximum value. -i-</p> |
