Found in Popular Electronics from the 90s, this circuit detects modulated infrared radiation and serves as a test for remote controls. Infrared sensors equivalent to the one indicated can be used.
With the circuit shown, when the brightness of one lamp decreases, that of the other increases. There is...
We find this circuit in a 1970 publication. Transistors can be replaced by current equivalents and LDR is...
We find this battery charger in a 90's Hands-On Electronics. The charging current is 2 A and when...