This circuit is from an article about operations in a Radio Electronics magazine from around 1968. The transistors are types of the time and the power is not the greatest.
This simple lie detector was found in Popular Electronics. Transistors are commonly used. The...
This one-transistor alarm can be used with much more sensors than the two shown by the figure....
This circuit was obtained in a 1975 documentation. The maximum frequency depends on the diodes and the...