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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Heart Monitor –Transmitter (CB25406E)
This circuit was found in a Radio Electronics magazine from November 1991. The circuit operates at 2.2...
Integrated Amplifier TBA820L (CB19422E)
In the publication in which we found this circuit, it is suggested for applications in clandestine...
Automatic range selector (CB21525E)
This circuit was found in a 1966 EEE. It is intended for automatic switching of the measurement range of...