Physical layer protocols

thumb|USB 80 Gbit/s port logo Universal Serial Bus (USB) is an industry standard, developed by USB Implementers Forum (USB-IF), for digital data transmission and power delivery between many types of electronics. It specifies the architecture, in particular the physical interfaces, and communication protocols to and from hosts, such as personal computers, to and from peripheral devices, e.g. displays, keyboards, and mass storage devices, and to and from intermediate hubs, which multiply the number of a host's ports.

thumb|Acoustic coupler modems used a telephone handset as the audio medium, with the user dialing the desired number and then pressing the handset into the modem to complete the connection. These systems generally operated at a speed of 300 bits per second.

process of encoding information by varying properties of a periodic carrier waveform

thumb|A radio repeater retransmits a radio signal.

thumb|250px|Multiple low data rate signals are multiplexed over a single high-data-rate link, then demultiplexed at the other end.

an interface for connecting peripherals to computers, mainly used for connecting printers; was replaced by other technologies like USB and WLAN

Type of data transfer

digital network implementation in which two nodes establish a dedicated channel through the network before they communicate

proposal to carry IP traffic by birds

collection of standards for wired Ethernet

pattern used within a communications system to represent digital data

coding technique in communication technology

thumb|right|Single high-brightness Light-emitting diode|LED with a cheap [[loupe lens creates a bright narrow beam that can stream DVD-quality video over neighbourhoods. The red beam is invisible when observed outside of its unobstructed path.]] thumb|Twibright Ronja with diameter lenses, operating on a link using visible red light, max. range , with HPWT-BD00-E4000 transmitter LED. Installed on a rooftop, with its user posing to the right, in Czech Republic. thumb|right|Three bolts preloaded with pink rubber blocks facilitate fine adjustment of the optical head direction with a gear ratio 1:3

form of serial communication lacking synchronization control signals

A passband is the range of frequencies or wavelengths that can pass through a filter. For example, a radio receiver contains a bandpass filter to select the frequency of the desired radio signal out of all the radio waves picked up by its antenna. The passband of a receiver is the range of frequencies it can receive when it is tuned into the desired frequency as in a radio station or television channel.

REDIRECT Physical layer#PHY

thumb|260px|RS-449 pinout The RS-449 specification, also known as EIA-449 or TIA-449, defines the functional and mechanical characteristics of the interface between data terminal equipment, typically a computer, and data communications equipment, typically a modem or terminal server. The full title of the standard is EIA-449 General Purpose 37-Position and 9-Position Interface for Data Terminal Equipment and Data Circuit-Terminating Equipment Employing Serial Binary Data Interchange.

Serial communication with clock signal

thumb|X.21 adaptor for a Japanese NEC PC-98. X.21, also referred to as X21, is an interface specification for differential communications introduced in the mid-1970s by the CCITT, now ITU-T. X.21 was the first digital signaling interface developed. The connector specification is defined by the ISO document 4903.

LocalTalk is a particular implementation of the physical layer of the AppleTalk networking system from Apple Computer.

term in physics

use of Ethernet between a telecommunications company and a customer's premises

widely used serial interface standard for industrial applications between a master (e.g. controller) and a slave (e.g. sensor)

ethernet physical layers using twisted-pair cables