This circuit is from an old documentation, but perfectly current. In place of the battery, 2 or 4 small cells can be used.
This low frequency circuit was found in documentation from the 1980s. The values of R and C...
This source for devices for automotive use was found in a 1985 documentation. The power...
Found on Popular Electronics in the 1980s, this circuit detects a change in air pressure using a...