Found in the American 73 magazine for radio amateurs, this circuit can test common quartz crystals. The circuit includes the power supply.
This circuit of a few tens of milliwatts of power requires a single source. We found it in a Radio...
This circuit is suggested by Texas Instruments in his Optoelectronics Sourcebook. The transistors...
This circuit used in signaling for boats, cars or barriers was found in a 1980s documentation. It still...