Found in a 1980s American documentation, this circuit has a current consumption of only 1 mA. The crystal can be from 100 kHz up to a few megahertz.
This circuit is from a 1979 publication. The sensor consists of plates or screens that, when...
The circuit is from a Radio Electronics from August 1989. The cells used at that time did not have...
The automatic modulated siren circuit shown in the figure really produces an interesting sound...