Modulated infrared emitter (CB7251E)

Found in a 1968 Mullard manual, this circuit can function as an infrared audio link. The transistors can be the BC548.

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Delayed SCR trigger (CB19336E)
The circuit shown is from an old European publication. In it we have the way to activate a relay...
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We found this circuit in a European publication from the 1990s. Transistors are still common types...
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