This circuit protects the speaker from dangerous direct currents that could damage it. The circuit is from an Electronics Experimenter Handbook 1993 edition.
This oscillator can generate signals from 100 kHz to more than 50 MHz depending on the crystal used...
Found in a 1980s American documentation, this circuit appears with variations elsewhere in this...
This circuit was obtained in a 1969 documentation. The circuit modulates both the emitter current and...