Very strong audio spikes in a headset can damage the ear. This circuit, from a 90s Popular Electronics cuts them, being originally indicated to operate with an integrated amplifier of the time.
The oscillator shown in the figure can generate signals up to 500 kHz and has good stability. Coil...
Found in a 1960s RCA manual, this circuit uses components from the era. For the indicated circuit R1 is...
This circuit by Ferranti, in a 1967 publication, is intended for reading perforated tapes. The...