A fun patent to wrap your head around

[Al Kossow]

5287534 "Correcting Crossover Distortion Produced When Analog Signal Thresholds Are Used To Remove Noise From Signal"

It describes the DEC CXM04 board for the DS550 communications server, which inserts itself between an IBM establishment
controller and a control unit (coax) terminal so the CUT can pretend it's a serial terminal to VAXen without dropping
the polled connection to the IBM mainframe.

weird..