Speedometer Cars https://www.bouldercreekengineering.com/products.php I ordered a speedometer car from Train Electronics.The first product was a scale speedometer, with trackside sensors.For the wireless version, the speed sensor and transmitting electronics goes into a piece of rolling stock, and the trackside electronics picks up the signal and displays it.I've added an optional sensor for track voltage, since I run DCC, I thought it might be nice to determine if I can see voltage drops, which might indicate poor power delivers, bad joiners, etc.Here's a picture of the wireless receiver and display:The car itselfNormally it was put in a Hartland car. I bought a USAT 70 ton hopper, and figured the coal load would be easy to pop off to get at the electronics, but they would be hidden most of the time.Since I wanted to sense the voltage, I needed good pickups. I used the LGB BB wheels. Well, they raise the body too much. So to body mount Kadee 830's I put 2 shims down the length of the draft gear box. It worked out to a .125" and a .060" together to get the height correct. You can just see part of the draft gearbox.I mounted the pickup wheels inboard at each end so the wires would be hidden. Dave makes the encoder disc, and mounts it and the sensor:The electronics are added inside, you can see the battery and the transmitter:All I can say is that it works even better than I thought, and Dave is great to work with. Here's a link to his site with more pictures: Click Here to see the pictures Setting: The same unit can be configured to operate both as a wireless and a wired unit. To switch between modes hold the MENU button for several seconds when the main copyright screen is displayed. WIRELESS NOW=0 or NOW =1 will be displayed. Continue holding the MENU button until the unit goes to the next screen. If it was set for wireless (NOW=1) it will switch to wired mode (NOW=0) and visa versa. https://www.bouldercreekengineering.com/rollby.php