This simple circuit for headphones or small speakers was found in documentation from the 90s. The circuit works with voltages from 5 to 9 V and has good gain.
This circuit is suitable for SSB modulation and was obtained from an amateur radio documentation from...
This circuit was obtained in a 90’s Popular Electronics. The operators admit equivalents such as...
This 7400 TTL circuit has a memory, keeping the LED on when a pulse is detected. The circuit must be...