Created: Feb 19, 2014
No description available.
U1 and U2 are two sections of a quad comparator. The first, U1, functions as an amplifier and detector. Resistors R5 and R6 set the gain at 100; the output of U1 is an open collector to negative-peak-rectify the output with a decay time constant determined by R9 and C3. This dc output is then compared with the reference level selected by R8. U2 triggers switch Q1, and an LED inserted in the base drive of Q1 gives visual indication of switch closure.