Found in a 1964 Electronic Design this circuit makes use of components of the era. The output is 2 V peak to peak and the input is 2 V. The maximum frequency depends on the employed components.
This circuit was obtained from an old American documentation, and practically any general-purpose transistor...
This circuit is intended for monitoring an environment. It fires a relay with a sound, but only if...
This circuit is from an old documentation, but perfectly current. In place of the battery, 2 or 4...