The major functions and services performed by the physical layer are:
- Bit-by-bit node-to-node delivery
- Providing a standardized interface to physical transmission media, including
- Mechanical specification of electrical connectors and cables, for example maximum cable length
- Electrical specification of transmission line signal level and impedance
- Radio interface, including electromagnetic spectrum frequency allocation and specification of signal strength, analog bandwidth, etc.
- Specifications for IR over optical fiber or a wireless IR communication link
- Modulation
- Line coding
- Bit synchronization in synchronous serial communication
- Start-stop signalling and flow control in asynchronous serial communication
- Circuit mode multiplexing,[citation needed] as opposed to statistical multiplexing performed at the higher level
- Establishment and termination of circuit switched connections
- Carrier sense and collision detection utilized by some level 2 multiple access protocols
- Equalization filtering, training sequences, pulse shaping and other signal processing of physical signals
- Forward error correction,[citation needed] for example bitwise convolutional coding
- Bit-interleaving and other channel coding
The physical layer is also concerned with
- Point-to-point, multipoint or point-to-multipoint line configuration
- Physical network topology, for example bus, ring, mesh or star network
- Serial or parallel communication
- Simplex, half duplex or full duplex transmission mode
- Autonegotiation
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