The clipping circuit does not have energy storage elements like capacitors but it includes both resistors and transistors. This circuit is normally used for the selection in the transmission purpose. The ability of diodes to allow the flow of current in only one direction. A diode is best tested by measuring the voltage drop across the diode when it is forward-biased. A forward-biased diode acts as a closed switch, permitting current to flow. No voltage exists at the diode but voltage may be present in the circuit due to charged capacitors.