Found in a 1964 CQ magazine this circuit consists of an automatic telegraphic key, providing the correct duration for points and dashes. The circuit can be made with a current PNP transistor.
Found in documentation from the 1980s, this amplifier uses an integrated circuit from the time....
The purpose of this circuit is to monitor the operation of an alternator in cars with a 12 V...
High selectivity filters can be obtained by combining same frequency crystals in series as shown...