Coding schemes are used to reduce the interference from ambient light and other noise sources. Although, there are many coding schemes only three are commonly used: bi-phasing code, pulse distance code, and pulse length code. These codes are transmitted from the remote control unit at several possible carrier frequencies ranging from 30 kHz to 56 kHz. When the "volume up" button on a remote control is pushed, the LED sends out a series of light pulses that correspond to the binary "volume up" command.  The signal also includes a start and stop bit and an address for the device being controlled. The infrared receiver on the TV picks up the light pluses and converts them back into an electrical signal. It then passes this signal to the microprocessor which verifies the address and increases the volume.