This filter configuration used in telecommunications uses 4 Jaumnann crystals that are interesting for low and medium frequencies. The circuit is from an 80's documentation.
Found in a PE Hobbyst Handbook, this circuit checks if there is voltage in a power outlet by...
This circuit was found in an article in Electronics Now magazine from June 1998. The sensor...
This circuit generates an FM signal of 4.7 or 10.7 MHz for audio signals on analog TV or FM, with...