What is the main responsibility of the Physical Layer in the OSI model?

The primary responsibility of the Physical Layer in the OSI model is to transmit raw bits over a physical medium. This layer focuses on the transmission and reception of the unstructured raw data bits over a physical connection. It defines the hardware specifications of the various physical devices, including cables, switches, and other networking equipment, as well as the electrical signals, light signals, or radio frequencies that carry the data.

By ensuring that the physical transmission of data is efficient and reliable, the Physical Layer establishes a critical foundation for the higher layers of the OSI model which manage data formatting, error detection, and protocol configurations. While other layers handle various aspects like data integrity, compression, and flow control, the Physical Layer is solely focused on the mechanics of enabling communication through a medium, ensuring that the bits are effectively sent and received.