The circuit is from the manual of the integrated circuit used in the excitation of power transistors. The 30 V symmetrical supply should have a few amps of capacity.
This busy line indicator is very simple, serving for analog lines. The supply is made by two...
This circuit was found in an 80's Electronic Engineering. The circuit uses operatives of the time...
Other operational amplifiers series, such as the MC34072, MC34074, MC35071, MC35072, MC35074 d...