What are the typical signals for the TDR

A little bit simpler discussion

related to TELECOM line splices and so forth.

good theoretical introduction to a avalanche

good tutorial on avalanch

old standby with slow rise time

This simple tdr in use. uses a 74AC14

Here is a short discussion of SWR

here is a discussion about using a micro to triger a high speed ADC for sensing

http://www.ecnmag.com/articles/2009/07/low-cost-high-resolution-time-measurement-application

Looking at a fuel probe on the end of a shielded wire:

toddheffley.com