The point is when using the generator to briefly input a signal at various points along the signal path of an amp, for fault tracing, to not have any DC of the inject point going backwords into the generator, and thus killing the DC coupled output section in the generator. Proper 'measurements' should be injected at the input.
Quite some years ago, we used to build what we called a 'signal injector', - a fairly simple oscillator with short pulses and a freq. of about 1 khz - not important at all. Output was a ground clip and a needle point fed through a capacitor. Size used to be like an oversized felt tip marker. The trick was to use this to briefly inject a harmonically rich signal into the signal path of an amp, at varius points. It even worked quite well in the RF section on AM and short wave radios. It could also be accompanied by a signal tracer, - a small ampifier sometimes with a very simple diode detector for in the use RF section of radios. If anyone is interrested in this very simple but effective tool, schmatics should be all over the internet.......
WIth todays components, it should be possibel to getit down to ball point size...
