This 4-channel mixer amplifier was found in an American publication from 1947. The circuit uses counterphase output tubes and a transformer power source.
With this circuit we can activate a relay with a simple touch on the sensor. The relay can be 6 or...
This circuit was obtained in a 1979 publication. The operational amplifier is of the type with...
Found in a 1980s German publication, this circuit tests batteries by type. The circuit is based on a...