Morley Pedals is the name of a guitar effects pedal company, famous for manufacturing wah-wah pedals and other treadle type effects for guitar. Morley pedals use electro-optical circuitry rather than a potentiometer to control the effect. The foot treadle controls a shutter inside the pedal that in turn controls the amount of light reaching a Light Dependent Resistor (LDR). The advantage to this system is that there are no potentiometers in the signal path to wear out or become "scratchy sounding" over time. Electro-optical circuitry is used throughout the classic Morley pedal line, which includes or has included volume pedals, delay pedals, chorus and phaser pedals, and many others.