Modulation monitor (CB8216E)

Found in a 90s Popular Electronics this circuit monitors the modulation of transmitters indicating 50%. 80% and 100% modulation.

Locked Micro Alarm (CB1513E)
This circuit locks when the sensors are opened. The relay can be 6 or 12 V depending on the power...
Transistor Tester (CB1409E )
The indicator instrument of this transistor tester, from an Argentine publication of the 1970s,...
7-segment LCD driver (CB7556E)
Found in American documentation from the 90s, this circuit uses TTL technology and is therefore...