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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Second Order Voice Filter (CB6544E)
Found on an 80's Radio Electronics, this circuit is designed to pass the 300 to 34,000 Hz voice...
10 W amplifier for servo (CB8949E)
This circuit was found in a 1960s Motorola documentation. Transistors are types of the time and...
Improved Multivibrator (CB12061E)
This circuit is from an English publication from 1978. The transistors can be the BC548 and the...