Alarm Buzzer (CB24392E)

This circuit was found in July 1975 Radio Electronics magazine. Power depends on the trigger transistor and the effects of capacitors C1 and C2.

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Temperature Controller (CB6016E)
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TTL Interface Shield (CB19757E)
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Operational with Hysteresis LM309 (CB15103E)
In the figure we have the way to add hysteresis to an operational amplifier. The relationship...