IBM, sonic delay lines, and the history of the 80×24 display

VT100s.

This is very timely for me. I'm working on a personal project of a terminal with 40x25 resolution and having to work around those limitations for displaying 80x24 content.

One of the most interesting features of the 2260 is the sonic delay lines used for pixel storage. Bits were stored as sound pulses sent into a nickel wire, about 50 feet long. The pulses traveled through the wire and came out the other end exactly 5.5545 milliseconds later. By sending a pulse (or not sending a pulse for a 0) every 500 nanoseconds, the wire held 11,008 bits. A pair of wires created a buffer that held the pixels for 480 characters.

This feels like there is a tiny bit of overlap with semi-modern DRAM (transistor based) that requires refresh intervals to keep the volatile contents active.