IR remote control emitter (CB7020E)

This circuit was found in 1980's Radio Electronics. The circuit produces a 1500 Hz modulate 35 kHz. The components used are still common.

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CMOS Alarm (CB4803E)
This circuit is from Popular Electronics of the 90's. It makes use of NO and NC sensors. The relay...
Modulator for rectangular signals (CB21630E)
Based on TTL logic this circuit can vary both the frequency and the pulse width of a rectangular signal....
Interval for windshield wiper (CB22145E)
This circuit was found in an old English publication. The circuit makes use of general-purpose transistors....