Found in a 1970 EEE, this circuit can be applied to TTL ports. The supply is 5 V and the frequency, which depends on the crystal, can be between 1 and 3 MHz.
This current meter with many scales was found in a 80s American documentation. The operational amplifier...
This dimmer, from an old publication, can use almost any triac and in shooting a neon lamp. The...
We found this circuit in a 1975 publication. The circuit can be made with more modern equivalent...