This circuit was found in Raytheon's 1967 documentation. The circuit uses an operating of the era, but the configuration can be applied to modern operational amplifiers.
This simple Philips circuit from the 1960s can use any general-purpose transistor. The signal is...
This setting appears multiple times on the site from different sources. This is from a 2000 manual...
This “people detector” with pyroelectric sensor was found in the April 1991 issue of Radio...