Some folks were asking me about the AGHR telemetry train (the one I was using to debug in SD3R a few weeks back) so here it is in video form.
It's fairly straight forward. The bitscope is asked to capture 12000 points on the first rising edge it sees over 3V (big enough to ignore most TMCC situations). It then figures out which part of the trace has packet in it, calculates the excursion and sends it to an LCD driven by an arduino board over USB/virtual serial. The C code I wrote to do it all is attached which should work fine under most linux distributions. It also contains the functions to stream the result out to the arduino board. Unfortunately, I'm not organized and I can't find a copy of the .ino running on the arduino, but it's pretty straight forward to just get a string and drive an LCD, so I'm sure everyone can figure it out if they have to.
The main analog parts needed are a bitscope USB oscilloscope to capture the waveforms and the filter from the old post. Then that feeds a raspberry pi host computer which runs the C program to capture the waveforms and does the calculations. For convenience I send the voltages out to an LCD screen controlled by an sparkfun arduino board. Added up the whole thing + the flat car is about $250-300 depending on how good of a deal you get.
The other cool thing the telemetry train does is measure forces with an accelormeter in the wheel truck. You can read more about that in the other post.
It's actually quite a useful device for how simple it is.