The selected circuit was found in GE's 1977 semiconductor manual. 3N84 is a controlled silicon switch and SCRs support equivalents. The transistor can be a BC558, depending on the supply voltage.
Based on an integrated circuit CA31062 which consists of a photosensor, this circuit was obtained from...
This 500 V line current monitor with the LTC6101 was obtained from Linear Technology's own 2005...
This is one of many timer settings with the 555 found on this site. This is the traditional...