This circuit was obtained in a magazine for radio amateurs 73 of the 90s. The circuit is based on the XR2206, which is not a component found easily today.
This series sensor circuit is from 1995 Popular Electronics. The circuit can use any SCR and the...
The circuit is a multivibrator version using two NPN general purpose transistor. This circuit can...
This circuit is from 1976 documentation. It uses the operational amplifier 709 which is no longer...