The physical layer standards address three functional areas:
- Physical components: Includes electronic hardware devices, media, and connectors that transmit and carry the signals to represent the bits.
- Frame encoding technique: Refers to the method of converting a stream of data bits into a predefined code. Codes are groupings of bits used to provide a predictable pattern that can be recognized by both the sender and the receiver. Using predictable patterns helps to distinguish data bits from control bits and provide better media error detection.
- Signaling method: Refers to the electrical, optical, or wireless signals that represent the "1" and "0" on the media. The physical layer standards must define what type of signal represents a "1" and a "0". This can be as simple as a change in the level of an electrical signal or optical pulse or a more complex signaling method. Signalling method varies depending on the encoding scheme.
The table in the figure displays a few examples of physical components, frame encoding techniques, and signalling methods used by copper, fiber-optic, and wireless media.