This charger for automotive use provides a 0.42 A output current. We find it in an American documentation from the 90's. The transistor must have a heat sink.
Using a 741 op-amp this circuit high-pass to 10 kHz was found in the February 1995 issue of...
This circuit produces an intermittent ring tone being triggered directly by the telephone line. However,...
This two-port configuration of the 4001 was found in the April 1988 issue of Radio Electronics magazine....