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Dual-purpose test-instrument, Very simple circuitry, 1.5V Battery-operated. This simple circuit generates narrow pulses at about 700-800Hz frequency. The pulses, containing harmonics up to the MHz region, can be injected into audio or radio-frequency stages of amplifiers, receivers and the like for testing purposes. A high-pitched tone can be heard from the speaker of the device under test when all is working properly. The clip must be connected to the ground of the device under test, touching with the probe the different stages of the circuit, starting from the last stage and going up towards the first. When the tone is no longer heard, the defective stage has been found. Connecting an earclip or headphone to J1, the circuit will automatically change into a two-stage amplifier and any audio signal coming from the device under test and picked-up by the probe will be heard through the headphones. The testing of a circuit should be made in the reverse manner, i.e. starting from the first...

General Description: AN7516SH has a speaker power amplifier, head phone power amplifier, line amplifier, electric volume, 3-dimensional Spatializer and a bass boost circuit for notebook PC. This IC adopts a small thin package, enabling compact and high integrated set. Block Diagram: AN7516SH Audio signal processing IC for notebook PC Datasheet for AN7516SH:

This circuit is wealthy in harmonics and is good for testing amplifier circuits. to seek out a fault in an amplifier, connect the planet clip to the 0v rail and move through each stage, beginning at the speaker. a rise in volume ought to be heard at every preceding stage. This Injector will bear the IF stages of radios and FM sound sections in TV's. to Index Signal Injector Circuit Diagram   http://streampowers.blogspot.com/2012/07/signal-injector.html 

Well, our meetings take place on Wednesdays at 10:30 (sharp). A radio controlled clock is used to determine whether you are late (and must bring a cake next time) or not. Unfortunately the identical radio controlled clock in my office always shows a different time :-( After baking a lot of cakes, I thought about synchronising these disreputable clocks …[ ]