About 10 years ago, I hardwired the Valentine One (V1) radar detector into my car. The setup involved tapping into the power supply behind the radio and wiring from the radio over to the driver's side, up the A pillar and along the top of the windshield, to the rear view mirror, with the V1 sitting on top of the mirror using suction cups. Over time, the suction cups would occasionally lose grip and leave the V1 dangling off the connecting wire. Recently, the stresses resulted in the wire snapping and I had to replace the wire.
What should have been a straightforward affair turned out to be a multi-hour ordeal. The V1 requires simple telephone wire with RJ11 connectors for wiring. A simple four conductor wire does the trick. My first purchase of a four conductor wire didn't work. Being misled by forum posts, I get a six conductor and eight conductor wire, but neither worked. After some logically checking of voltages and resistance, with my friend's help, I was able to figure out that the problem was with the fuse in my hardwire setup. After replacing the fuse and using a regular four conductor setup, I was able to get the wiring going again.
In short, here are the parts required: