Universal tester, puzzled

It is meant to produce a tone the frequency of which will depend on the voltage seen across the test probes. It loads the external circuit so will not be good for probing voltages inside an electronic circuit but might be used to distinguish a flat battery from a good battery.

piglet

My bad, as drawn it is the *resistance* of whatever is between the test probes that will affect the tone.

piglet

You have first to decide whether trust the schematic or the text. The IC on the schematic is 4060 and in the text 4046 (which may be more trustworthy).

You have to take more grains of salt with the schematics from that site.

well yes, some interesting ideas but some iffy circuits.

NT