Outlet test (CB7952E)

Found in a PE Hobbyst Handbook, this circuit checks if there is voltage in a power outlet by emitting sound and lighting an LED.

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Fast photoelectric relay (CB23760E)
This fast trigger circuit allows the counting of up to 300 pulses per minute. The circuit is from...
Old Intercom (CB18542E)
This intercom uses transistors from the 60s. It was found in a Japanese publication at the time....
Flasher for Mobilete (CB18809E)
This circuit is from an old publication from the 90s, but it can be adapted to operate with LEDs....