Physical Layer Devices

Physical layer devices handle functions such as signal transmission, reception, conversion, and regeneration, without interpreting the meaning of the data. Based on their functionality, these devices can be categorized into pure physical layer devices, which work only at Layer 1, and partially physical layer devices, which also perform functions at higher layers such as data link layer (Layer 2).

1. Pure Physical Layer Devices

Pure physical layer devices function exclusively at Layer 1. They are not aware of MAC addresses or data formats—these devices simply transmit, regenerate, or convert physical signals.

Pure Physical Layer Devices: Table

Device Function
Hub Broadcasts electrical signals to all ports. No data filtering or traffic management.
Repeater Regenerates and amplifies signals to overcome attenuation over long distances.
Cables Provide the medium for data transmission (e.g., coaxial, twisted pair, fiber optic).
Connectors Enable physical connections between network components (e.g., RJ-45, SC, ST).
Transceivers Combine transmitter and receiver circuits for signal transmission.
Media Converters Convert signals from one physical medium to another (e.g., copper to fiber).

Partially physical layer devices operate at Layer 1 but also perform functions at higher layers, typically Layer 2 (Data Link Layer). These devices handle physical signal transmission as well as some form of data framing, addressing, or protocol control.

Partially Physical Layer Devices: Table

Device Physical Layer Role Higher Layer Functions
NIC (Network Interface Card) Sends and receives raw electrical or optical signals Handles MAC addressing and framing (Layer 2)
Modem Modulates and demodulates digital and analog signals May include error correction and flow control (Layer 2)
Wireless Access Point Transmits/receives radio signals Processes MAC addresses and may route traffic (Layer 2/3)