This circuit uses a crystal phone and can be built with more modern transistors like the BC548. The original circuit is from a 1979 publication and is powered with only two AA or AAA batteries.
This circuit with two operating modes was found in the September 1989 issue of Radio Electronics...
This TTL divider divide by 0 to 9 the frequency of a signal applied to its input. Maximum...
This circuit can be used for signaling a panel with a common incandescent lamp. The lamp will...