This circuit was obtained in an Electronics World of 1968. The operational amplifiers ones are types of the time, no longer used today. The circuit responds from less than 20 Hz.
This circuit can be used in demonstrations or science fairs. The circuit uses headphones and can...
We found this wiretapping circuit in a publication from the 90s. The circuit allows the cable...
This circuit uses a resonant reed switch at the trigger frequency. The circuit is from General...