We found this circuit in a documentation from the 70s. Semiconductors are from the era and can be replaced by modern equivalents.
This circuit with 5 times gain was found in European documentation from the 1980s. The input and...
This circuit was found in a 1987 magazine. It measures the pulse rate produced by a cardiac...
This simple intermittent siren circuit was found in a 1989 documentation. Both the intermittent and...