Found in 1967 Raytheon documentation, this circuit uses a company coupler consisting of a lamp and an LDR. The transistor is according to the load current.
Using a 4017 as a base, this circuit from a 1990s Popular Electronics generates low-frequency...
Approaching the hand or an object to the sensor of this circuit, the relay closes its contacts. The...
This 1967 General Electric circuit makes use of an array of 3 (integrated) transistors for an...