dialupmodems

Dial-up modems are devices that allow computers to connect to the public switched telephone network (PSTN) by converting digital data into analog sounds for transmission over telephone lines, and then converting received analog signals back into digital data. They were the standard method for home and small-business internet access from the 1980s through the early 2000s, before broadband technologies became widespread.

How they work: The user dials a phone number to reach an Internet Service Provider's modem pool. After a handshake, the two modems agree on a data signaling rate and a protocol, commonly PPP (point-to-point protocol) or SLIP. The connection uses ordinary copper telephone lines and produces audible tones as the modems train and synchronize. Data is transmitted using modulation techniques such as frequency-shift keying (FSK) in early models and more advanced multi-tone modulations in later ones.

Speeds and standards: Early consumer modems operated at 300 baud, followed by speeds of 1200, 2400, and 9600 bps, then 14.4, 28.8, and 33.6 kbps. The term 56 kbps is associated with downstream speed limits achievable by consumer dial-up services using ITU-T standards such as V.90; upstream speeds were typically lower. Modern dial-up modems commonly supported V.92, which offered faster connect times and improved upstream throughput in many scenarios.

Decline and legacy: Dial-up internet access declined rapidly after broadband became widely available in the late 1990s and 2000s. It remains in limited use in some rural or remote areas, for fax services, or as a backup connectivity option. The technology is documented in ITU recommendations and remains of historical interest for understanding early consumer networking.