With distortion of less than 1 dB from 10 Hz to 20 kHz this circuit was found in the December 1972 issue of Radio Electronics magazine. The amplifier is a type that preceded the 741, the 709.
This circuit is from 1990 documentation. When we press D1 the lamp remains on for a time interval that...
This 1995 circuit uses interruption sensors or NC connected in series in any quantity. With the...
This circuit from a Radio Electronics magazine from June 1969 already shows the use of the newly...