This crystal or galena radio uses a germanium diode. C1 is an old radio variable and L1 has 100 turns of 26 or 28 wire in a 1 inch PVC pipe. The antenna must be a long wire.
The trip circuit for this alarm is given in CB16765E. The circuit uses common components and acts...
This circuit is from an old American publication from 1970, but it can be assembled with a BF494...
This circuit found in 1969 Popular Electronics is used to power a gas laser. The circuit produces...