This circuit works on analog I/O ports and was suggested by an Electronic Design from the 90s. It can be used to work as a shield in projects with microcontrollers.
This circuit is from a Ferranti publication of 1968. The circuit generates a signal according to the...
This simple alarm using only transistors was found in a 1990 publication. It can be powered by D...
This circuit originally appeared in a publication of 1997. With the changes, the circuit can be...