Timed Alarm (CB6423E)

We found this circuit in a 90's Popular Electronics. The circuit produces a loud sound if S2 is not pressed to reset.

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Basic LM3914 (CC25109E)
This is the basic full-scale circuit of an LM3914 for voltage measurement or voltage triggering and...
1kHz Triggered Oscillator 555 (CB25513E)
We found this circuit in the October 1992 Radio Electronics magazine. The frequency is given by C1...
Ultrasonic Generator (CB6891E)
Although most common piezoelectric transducers have a reduction in performance at frequencies...