This circuit was obtained in a QST magazine from the 90s. The circuit makes use of components that are uncommon today. The circuit includes a gain selection switch.
This circuit detects light variations using two LDRs as sensors. Operational amplifiers and...
The circuit shown consists of a power stage for relay excitation. 2N3053 can be a BD135 and 2N406...
This circuit was found in Mullard's 1960s transistor manual. The circuit uses germanium...