Found in a 1980s American documentation, this circuit can use a SCR and a general-purpose transistor. R2 is 1 M and R1 is 10k. The capacitor is 47 uF.
This two-tone decoder has a bandwidth of 24%. The circuit is from a 1994 Electronics Now. The...
Bike speedometer (CB20497E) This circuit can be powered by a solar cell. The circuit is from a...
This is a typical common collector amplifier step configuration. The transistor can be used...