Physical Layer - The equipment
The first, or physical, layer of the open systems interconnection (OSI) model. Delivers data across a network link. This layer must regulate signaling and keep the signal strong. Hubs, repeaters and concentrators operate at Layer 1. All packets received are repeated on the wire.
Physical layer of the OSI reference model defined in ITU X.200. It is responsible for the electric signal being sent and received. This can be viewed as a bit stream coming in, and going out, of the system. Scope must be considered when using this term. For example, Layer 1 on a T1 is 1.544 Mbps but Layer 1 on a DS-0 timeslot in the T1 is 64 kbps.
In the (OSI) model, the physical layer which represents the hardware used for communication.