- The physical layer considers how to transmit data bit streams on the transmission media connecting various computers , rather than referring to specific transmission media.
- The role of the physical layer is to shield the differences between different transmission media and communication means as much as possible.
- The protocol used for the physical layer is also often referred to as the physical layer procedure .
In fact, the physical layer protocol is the physical layer protocol, but people used the term "protocol" before the term "protocol" appeared.
The main tasks of the physical layer
Main task: Determine some characteristics of the interface with the transmission medium .
Mechanical characteristics : Indicate the shape and size of connectors used in the interface, the number and arrangement of leads, fixing and locking devices, etc.
Electrical Characteristics : Indicates the range of voltages present on each wire of the interface cable.
Functional characteristics : Indicate what meaning the voltage of a certain level appears on a certain line.
Process characteristics : Indicate the sequence of occurrence of various possible events for different functions.