A proximity sensor is a sensor that can detect the presence of nearby objects without any physical contact. A capacitive proximity sensor is made from a copper trace tuned for a higher sensitivity than capacitive buttons. Such a sensor can be used to add wake-on-approach feature in end products and save power. Signal-to-noise ratio, also called SNR, is the ratio of the sensor signal, when touched, to the noise signal of an untouched sensor. LED Control Signal is a signal controlled by a register used to turn an LED ON or OFF. A general-purpose output (GPO) is an output pin on a chip that the user can configure to handle a variety of tasks, such as outputting an LED Control Signal. Parasitic capacitance (Cp) is the intrinsic capacitance of the PC board trace that connects to a capacitive button. It reduces the sensitivity of a capacitive button. The shield electrode is the copper fill around sensors to prevent false touches from exposure to water or other liquids. The guard sensor is the copper trace around shield electrodes which is used to detect a water stream. Lastly, water tolerance is the ability of capacitive buttons to work properly in the presence of water droplets, a water stream, or mist.