This amplified speaker is from a Radio Electronics from September 1988. The power integrated circuit is from that time and the other components are still common today.
The time the output is high (1) of a TLCSSB in the astable configuration depends on Ra and C. The...
The adjustment of the maximum load voltage is made in the trimpot. The circuit is from 1994...
This circuit from a 1967 documentation generates 2.5 Hz signals depending on the capacitors used,...