Utility that detects short circuits doing to know it in sonorous form.
This utility turn on when the resistance between the test
ends is of the order of the miliohmios. IC1A is connected like astable
multivibrator. R1 and C1 approximately fix their frequency of
oscillation to 1kHz, assumming that in IC exists a virtual mass
(potential of zero volts). T1 and T2 amplify the exhaust stream of
IC1A and inject a square signal of 20 volts tip to tip of amplitude to
R4. This causes that 100mA flows a current by resistor saying of +/-.
R5 assures that the tension in the end never is superior to +/-0,1V.
IC1B controls the tension in the test ends. When the ends are in
opened circuit, the IC1B gain equals to relation R4/R5, which causes
that the exit of both amplifiers is equal. This does that the
loudspeaker, as is connected to the two exits, does not sound. If, on
the contrary, the ends are in short circuit, the exit of IC2B becomes low, causing that the oscillations of IC1A
arrive at the loudspeaker taking place therefore the sound.
I hope you can understand it :?
Components are this:
Resistors
R1=R2=R7=100kW 1/8W
R3=10kW 1/8W
R4=100W 2W
R5=R8=1W 1/8W
R6=680W 1W
Capacitors
C1=22 nF disc
C2=100 mF 25V electrolytic
semiconductors
IC1=LM148
T1=2N3904
T2=2N3906