This circuit was obtained from a Radio Electronics in February 1965. The circuit uses two transistors from the time and can be created with modern equivalent transistors.
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...