Retro Technology

When traditional dial-up modems communicate, they encode digital bits as screechy analog tones that would then be carried over phone lines originally designed for human voices. It’s an imperfect way of doing things, but it was the most practical way of networking computers in the olden days. There was already a telephone line in just about every house and business, so it made sense to use them as a conduit to get computers online.

For years, speeds ticked up as modem manufacturers ratified new, faster modulation schemes. Speeds eventually reached 33.6 kbps which was believed to be near the theoretical maximum speed possible over standard telephone lines. This largely came down to the Shannon limit of typical phone lines—basically, with the amount of noise on a given line, and viable error correcting methods, there was a maximum speed at which data could reliably be transferred.

In the late 1990s, though, everything changed. 56 kbps modems started flooding the market as rival manufacturers vied to have the fastest, most capable product on offer. The speed limits had been smashed. The answer lay not in breaking Shannon’s Law, but in exploiting a fundamental change that had quietly transformed the telephone network without the public ever noticing.