Replaced the trailer brake controller in the ‘73 today. It was time to upgrade! I was surprised to see that the old one was the same brand. Tekonsha has that market share pretty well locked up!
The original was almost steampunk - a hydraulic tee at the master cylinder allowed brake pressure to dictate how much voltage to send to the trailer by mechanically pushing the slider over, same as you could do by hand. My uncle pulled a 30’ travel trailer with it in the 80’s, I use it for my car trailer.
I’m prepping for a haul from Boston to Syracuse in a few weeks. Here’s an interesting tidbit - in MA, the max load for a trailer with no brakes is 10,000 lbs! In every other state, 1,500 is the limit.