This circuit was obtained from American documentation from the 1990s. The transformer can be a car ignition coil that works like an autotransformer. Q2 must be equipped with a heat sink.
This was one of the National Semiconductor clock modules very popular in the 70s and 80s. In the...
This circuit is from 2001 documentation, serving to multiplex stereo signals for FM transmitters. The...
EDN magazine in a 90's issue published this TTL technology debouncer flip flop circuit, in this...