This circuit is from old American documentation, using a regulator integrated circuit that is uncommon today. The diodes can be 1N4002 and the transformer has a 500mA secondary.
We found these circuits in a Popular Electronics from the 90s. The circuit has a simple low power...
This LED diode test is suggested by the Texas Instruments optoelectronics manual. The transformer current...
This RF monitor or field strength meter can use instruments from 100 uA to 1 mA full scale. The...