Vendor lineage
Codex - modems, and the mathematics underneath them
A company whose product was signal processing sold as a box, in the window a regulator had just opened.
Codex built high-speed modems in the years after the interconnect decisions made it lawful for somebody other than the telephone company to attach equipment to a line. Its work sat on the mathematical side of data communications - getting more bits through a voice-grade circuit than the circuit looked capable of carrying - which is a different discipline from the switching and multiplexing most of this timeline is about.
The modem is the product this period is most associated with and the one most often taken for granted. A voice line was engineered to carry speech, and everything above about 2,400 bits per second on one was won by signal processing rather than by better wire.
The company was later absorbed and the name eventually became Vanguard, which is why searching for it lands on a successor. That is the usual ending in this part of the timeline and it is recorded rather than smoothed over.