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 comes from an English publication of 1976, consisting of an experimental touch key....
This sophisticated circuit using a liquid crystal display was found in Radio Electronics from the...
This circuit was obtained from an old documentation, but as it uses still current components it can be...