The network physical layer is the lowest network layer in the Open System Interconnections (OSI) model. The primary concern of this layer is transmission of individual bits from one node to another over a physical medium.
In TCP/IP model, the physical layer and the data link layer are combined as the host - to - network layer.
The Open System Interconnections (OSI) model is a layered networking framework that conceptualizes how communications should be done between heterogeneous systems. The physical layer is its lowest layer.
The following diagram depicts the position of the physical layer where a transmission is done from a sending machine to a receiving machine.
Defining the physical characteristics and functions of the physical devices and interfaces so that transmission can occur
Specifying the number of pins in each of the devices as well as the purpose of each pin
Defining the process of bit - encoding, like, how many volts should represent a 0 bit and 1 bit in case of electrical signals
Laying out the transmission medium and type of signal for transmitting the bits, i.e. electrical pulses, optical pulses or radio signals
Determining the data transmission rate and the duration of a bit
Stating the topology, i.e. physical layout, of the network devices
Specifying the direction of transmission, i.e. whether the transmission is in simplex mode, half duplex mode or full duplex mode