Modem in the context of Conventional PCI

Data communication is the transfer of data over a point-to-point or point-to-multipoint communication channel. Data communication comprises data transmission and data reception and can be classified as analog transmission and digital communications.

Analog data communication conveys voice, data, image, signal or video information using a continuous signal, which varies in amplitude, phase, or some other property. In baseband analog transmission, messages are represented by a sequence of pulses by means of a line code; in passband analog transmission, they are communicated by a limited set of continuously varying waveforms, using a digital modulation method. Passband modulation and demodulation is carried out by modem equipment.

Dial-up Internet access is a form of Internet access that uses the facilities of the public switched telephone network (PSTN) to establish a connection to an Internet service provider (ISP) by dialing a telephone number on a conventional telephone line which could be connected using an RJ-11 connector. Dial-up connections use modems to decode audio signals into data to send to a router or computer, and to encode signals from the latter two devices to send to another modem at the ISP.

Dial-up Internet reached its peak popularity during the dot-com bubble. This was in large part because broadband Internet did not become widely used until well into the 2000s. Since then, most dial-up access has been replaced by broadband.

Integrated Services Digital Network (ISDN) is a set of communication standards for simultaneous digital transmission of voice, video, data, and other network services over the digitalised circuits of the public switched telephone network. Work on the standard began in 1980 at Bell Labs and was formally standardized in 1988 in the CCITT "Red Book". By the time the standard was released, newer networking systems with much greater speeds were available, and ISDN saw relatively little uptake in the wider market. One estimate suggests ISDN use peaked at a worldwide total of 25 million subscribers at a time when 1.3 billion analog lines were in use. ISDN has largely been replaced with digital subscriber line (DSL) systems of much higher performance.

Prior to ISDN, the telephone system consisted of digital links like T1/E1 on the long-distance lines between telephone company offices and analog signals on copper telephone wires to the customers, the "last mile". At the time, the network was viewed as a way to transport voice, with some special services available for data using additional equipment like modems or by providing a T1 on the customer's location. What became ISDN started as an effort to digitize the last mile, originally under the name "Public Switched Digital Capacity" (PSDC). This would allow call routing to be completed in an all-digital system, while also offering a separate data line. The Basic Rate Interface, or BRI, is the standard last-mile connection in the ISDN system, offering two 64 kbit/s "bearer" lines and a single 16 kbit/s "data" channel for commands and data.

In computing, input/output (I/O, i/o, or informally io or IO) is the communication between an information processing system, such as a computer, and the outside world, such as another computer system, peripherals, or a human operator. Inputs are the signals or data received by the system and outputs are the signals or data sent from it. The term can also be used as part of an action; to "perform I/O" is to perform an input or output operation.

I/O devices are the pieces of hardware used by a human (or other system) to communicate with a computer. For instance, a keyboard or computer mouse is an input device for a computer, while monitors and printers are output devices. Devices for communication between computers, such as modems and network cards, typically perform both input and output operations. Any interaction with the system by an interactor is an input and the reaction the system responds is called the output.

Demodulation is the process of extracting the original information-bearing signal from a carrier wave. A demodulator is an electronic circuit (or computer program in a software-defined radio) that is used to recover the information content from the modulated carrier wave. There are many types of signal modulation, and there are many types of demodulators. The signal output from a demodulator may represent sound (an analog audio signal), images (an analog video signal) or binary data (a digital signal).

These terms are traditionally used in connection with radio receivers, but many other systems use many kinds of demodulators. For example, in a modem, which is a contraction of the terms modulator/demodulator, a demodulator is used to extract a serial digital data stream from a carrier signal which is used to carry it through a telephone line, coaxial cable, or optical fiber.

A mobile broadband modem, also known as wireless modem or cellular modem, is a type of modem that allows a personal computer or a router to receive wireless Internet access via a mobile broadband connection instead of using telephone or cable television lines. A mobile Internet user can connect using a wireless modem to a wireless Internet service provider (ISP) to get Internet access.

In networking, a node (Latin: nodus, 'knot') is either a redistribution point or a communication endpoint within telecommunication networks or computer networks.

A physical network node is an electronic device that is attached to a network, and is capable of creating, receiving, or transmitting information over a communication channel. In data communication, a physical network node may either be data communication equipment (such as a modem, hub, bridge or switch) or data terminal equipment (such as a digital telephone handset, a printer or a host computer).

In telecommunications, a transmission system is a communication system that transmits a signal from one place to another. The signal can be an electrical, optical or radio signal. The goal of a transmission system is to transmit data accurately and efficiently from point A to point B over a distance, using a variety of technologies such as copper cable and fiber-optic cables, satellite links, and wireless communication technologies.

The International Telecommunication Union (ITU) and the European Telecommunications Standards Institute (ETSI) define a transmission system as the interface and medium through which peer physical layer entities transfer bits. It encompasses all the components and technologies involved in transmitting digital data from one location to another, including modems, cables, and other networking equipment.Some transmission systems contain multipliers, which amplify a signal prior to re-transmission, or regenerators, which attempt to reconstruct and re-shape the coded message before re-transmission.

In computing, bandwidth is the maximum rate of data transfer across a given path. Bandwidth may be characterized as network bandwidth, data bandwidth, or digital bandwidth.

This definition of bandwidth is in contrast to the field of signal processing, wireless communications, modem data transmission, digital communications, and electronics, in which bandwidth is used to refer to the signal bandwidth measured in hertz, meaning the frequency range between lowest and highest attainable frequency while meeting a well-defined impairment level in signal power. The actual bit rate that can be achieved depends not only on the signal bandwidth but also on the noise on the channel.

A bulletin board system (BBS), also called a computer bulletin board service (CBBS), is a computer server running software that allows users to connect to the system using a terminal program. Once logged in, the user performs functions such as uploading and downloading software and data, reading news and bulletins, and exchanging messages with other users through public message boards and sometimes via direct chatting. In the early 1980s, message networks such as FidoNet were developed to provide services such as NetMail, which is similar to internet-based email.

Many BBSes also offered online games in which users could compete with each other. BBSes with multiple phone lines often provided chat rooms, allowing users to interact with each other. Bulletin board systems were in many ways a precursor to the modern form of the World Wide Web, social networks, and other aspects of the Internet. Low-cost, high-performance asynchronous modems drove the use of online services and BBSes through the early 1990s. InfoWorld estimated that there were 60,000 BBSes serving 17 million users in the United States alone in 1994, a collective market much larger than major online services such as CompuServe.

Tethering or phone-as-modem (PAM) is the sharing of a mobile device's cellular data connection with other connected computers. It effectively turns the transmitting device into a modem to allow others to use its cellular network as a gateway for Internet access. The sharing can be done wirelessly over wireless LAN (Wi-Fi), Bluetooth, IrDA or by physical connection using a cable like USB. If tethering is done over Wi-Fi, the feature may be branded as a personal hotspot or mobile hotspot, and the transmitting mobile device would also act as a portable wireless access point (AP) which may also be protected using a password. Tethering over Bluetooth may use the Personal Area Networking (PAN) profile between paired devices, or alternatively the Dial-Up Networking (DUN) profile where the receiving device virtually dials the cellular network APN, typically using the number *99#.

The Apple II (stylized as apple ][) is a personal computer released by Apple Inc. in June 1977. It was one of the first successful mass-produced microcomputer products and is widely regarded as one of the most important personal computers of all time due to its role in popularizing home computing and influencing later software development.

The Apple II was designed primarily by Steve Wozniak. The system is based around the 8-bit MOS Technology 6502 microprocessor. Jerry Manock designed the foam-molded plastic case, Rod Holt developed the switching power supply, while Steve Jobs was not involved in the design of the computer. It was introduced by Jobs and Wozniak at the 1977 West Coast Computer Faire, and marks Apple's first launch of a computer aimed at a consumer market—branded toward American households rather than businessmen or computer hobbyists.