This circuit was found in an American documentation from 1975. The components of the time can no longer be found easily, but they can be tested equivalent.
Found in a 90s Popular Electronics, this circuit is interspersed between the filter and the...
This circuit is from an 80's documentation. The integrated circuit is from the time and the...
This circuit was found in a 80s American documentation. The zener diodes determine the points of...