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 circuit converts pulse frequency to current, which is indicated on an analog instrument. The...
This circuit is from 2005 Linear Technology documentation. The circuit applies to 12 V systems and...
This is a commercial circuit from the year 1958. Transistors are germanium types and transformers...