The TDC (Time to Digital Converter) was designed at PSL for the University of Wisconsin-Madison High Energy Physics Department. The TDC uses delay lines and ECL logic running at 100MHz (10nsec) to measure pulse arrival times with 1 nanosecond accuracy and resolution. Dozens of the boards were used at the Fermi National Accelerator Laboratory's Collider Detector Facility where they were connected to thousands of data channels from drift chambers to determine the trajectories of high energy particles. The TDC has 96 channels per board, is Fastbus compatible and was implemented in multiwire technology. The TDC was designed in the early 1980's, when personal computers ran at 5Mhz or less. The PSL TDC's were used to collect data that was ultimately instrumental in discovering the top quark.