We found this circuit in the 1964 RCA transistors manual. The sensor may be a common LDR and the transistor BC558. The relay has an operating voltage according to the power supply.
This circuit was originally designed for medical applications and biological experiments. The...
This circuit for a frequency of 40 kHz was found in an old Electronic Design. There were no...
The simple touch of the fingers on a sensor causes this circuit to drive a motor that goes into...