Flood alarm (CB7994E)

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

Telephone amplifier with LM386 IC (CB967E)
The circuit shown is only for analog telephone lines. I found it in Popular Electronics (1991). It...
Sensitive relay (CB22289E)
In this circuit from the 60s, the power supply is made with 22.5 V, which is the voltage of the...
Transient free divider by 8 (CB6825E)
This circuit is from 1967 General Electric documentation. It uses SUS which are not very common...