This circuit is one of many that the reader can find in this section for testing crystals. The circuit uses an indicator LED. Transistor Q1 determines the maximum crystal frequency that can be tested.
This simple circuit can be found in different versions on this website. The capacitor and resistor...
This configuration from an American publication from the 1970s shows how to use a pair of power...
The frequency of TTL square signal is divide by 5 with this circuit. Power supply is 5 V and the...