The Physical layer of the OSI model is concerned with the electrical, optical, and mechanical properties of the network, including elements such as voltage, media, connector types, signal regeneration, and so forth. The physical layer doesn’t actually alter packets, but rather acts as the transmission facility over which the actual bits (1’s and 0’s) are sent. This isn’t limited to plain old copper wire – it can include optical signals, radio waves, and infrared transmissions to name but a few. Examples of equipment found at the Physical layer include network cabling, hubs, and repeaters. A number of popular Physical layer standards are listed below.
Examples of Physical layer standards:
- High Speed Serial Interface (HSSI): High speed serial communications
- EIA/TIA-232: Low speed serial transmissions
- V.35: ITU-T serial transmission standard