The purpose of this circuit based on Maxim's MAX9022 is to find faults in multiple cables. The circuit provides an audible signal on a buzzer being powered by 3 small or AAA batteries.
This circuit was found in a publication in 2002 and can be powered by voltages from 5 to 12 V. The...
Found in an American 80's documentation, this circuit can use common FETs like the BF245 and cover...
Found in a publication for radio amateurs from the 1980s, this circuit amplifies signals in the 60...