This windshield wiper timer was obtained in an 80's Hands On. The transistor can be the BC548 and the relay is 12 V sensitive. The time is set to R3.
This circuit was obtained from an American 80's documentation. The balanced mixer can be shown in...
This circuit was found in an application note of the LTC1164 from Linear Technology of the 1990s....
This circuit has a type of bias called "virtual earth" providing good gain, given by R2. The...