The overload indicator consists of a window
comparator that measures the magnitude
of an a.f. signal. Two of the opamps
contained in an TL072 are supplied with a
reference voltage by potential divider
RI-R2-R3-P1. The outputs of the opamps
drive T1 via diodes D1 end D2 (that function
as half-wave rectifier). which in turn actuates
D3. Network R5-R6-C2 ensures that the
LED lights even during short signal peaks Capacitor C2 is charged fairly rapidly via D1
(or D2)and R6,after which it discharges slowly
via R6, R9 and the base-emitter junction of
T1. Capacitor C1 also contributes to the longer
lighting of the LED.
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