Flood alarm (CB7994E)

This circuit is from a 90s Popular Electronics. The transistors are of general use and the buzzer is a Sonalert type.

3-Channel Mixer (CB25702E)
This simple general-purpose transistor mixer was taken from an article in Electronics Now magazine in...
Logic Switch (CB22435E)
In the figure we have the configuration of a logic switch with the TTL 7400 circuit. The...
Voltage Level Detector (CB4660E)
This circuit is intended to trigger an alarm when the input voltage exceeds one value and to...