Using a 4046 PLL we found this circuit in the December 1989 issue of Radio Electronics magazine. The circuit operates at 220kHz, but this frequency can be changed by changing C3.
This circuit emits a sound when a magnetic field, of a magnet, for example, approaches the sensor....
This circuit is from the 1993 Motorola Linear Interface Circuits. The source does not have to be...
This circuit is from a 1964 Electronic Design. The transistors are from that time. They can be...