1-Ttube reflex receiver (T1555E)

This one-tube circuit is equivalent to the previous one. We find it in a 1924 book by Gernsback, Power is made by batteries.

Low Impedance Microphone Preamplifier (CB10675E)
This circuit is from a Popular Electronics from April 1991. The magazine no longer exists, but the...
Two-color indicator (CB7824E)
This two-color LED indicator was found in a Popular Electronics from the 90's. The transistor...
Micro Power LED (CB15111E)
This circuit causes an LED to flash at a frequency determined by the capacitor. The circuit has an...