The integrated circuits used in this configuration are not common today. The circuit is from the 1983 Intersil Databook. The indicator is 8 digits.
This circuit using an operational amplifier was found in old American documentation. It can be...
If the circuit oscillates, emitting sound, it is because the transistor is good. This simple...
Like the previous circuit, this is used in the analog part of the telephone lines. The same...