Metal Detector (CB21929E)

This two-transistor metal finder was found in a Raytheon manual from the 1950s. The transistors are germanium from the time.

Field intensity meter (CB7563E)
Found in a magazine 73 for radio amateurs, in a 90's edition, this circuit uses a general-purpose FET...
12V Lamp Flasher LM3909 (CB14284E)
The selected circuit causes a 12 V lamp with a current of up to 500 mA for the BD135 transistor to flash at...
Schmitt Trigger with 555 (CB25527E)
This is one of the many applications of the 555. We found it in the November 1992 Radio...