The physical layer is the lowest layer in the OSI reference model. It is in charge of establishing a physical connection between the devices. BITS of information are stored in the physical layer. It is in charge of sending individual bits from one node to another. When this layer receives data, it converts the signal received into 0s and 1s and sends them to the Data Link layer, which reassembles the frame.

The physical layer's FUNCTIONS are as follows:

• Bit synchronisation: A clock is provided by the physical layer, which allows the bits to be synchronised. This clock controls both the sender and the receiver, ensuring bit-level synchronisation.
• Bit rate control: The transmission rate, or the number of bits transferred PER second, is likewise DEFINED by the Physical layer.
• Physical topologies: The physical layer defines the arrangement of devices/nodes in a network, such as bus, star, or mesh topologies.
• Transmission mode: The physical layer also SPECIFIES how data is passed between the two linked devices. Simplex, half-duplex, and full-duplex transmission modes are available.