It is interesting to note other applications a quartz crystal has. Besides keeping the radio transmitter and receiver on frequency, crystal filters are used to accomplish the IF selectivity of receivers, notch filters, voice scramblers, and discriminators of receivers. Digital devices such as frequency counters, frequency synthesizers, digital clocks, and even the electronic watch you might be wearing are crystal controlled. Crystals may be found in wildlife tracking equipment, almost every computer, and most modems that are used by computers to communicate. Today, literally millions of people keep in touch with personal pagers and these units depend upon crystals to stay on frequency.
Crystals operate through the phenomenon known as piezoelectricity.
Other interesting adaptations of the piezoelectric effect include certain kinds of microphones, ear phones, phono pickup cartridges and ignition systems. As one can see, these small silver cans are likely to be found anywhere from model airplanes to spaceships, fishing boats to ocean liners, from a child's walkie talkie to satellites orbiting the earth. It is impossible to predict the future uses of crystals and, although the demise of it's use has been predicted for decades, it continues to be a vital part of the electronics industry. Therefore, a piezoelectric quartz crystal is a device that will produce an electrical output when mechanical pressure is applied. The substance quartz is a mineral and it's chemical makeup is silicon dioxide, SiO2.