Found in an RF Design from the 90's this circuit is intended for crystals of less than 1 MHz. Transistors are types of general use today.
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...