With respect to everyone discussing, you absolutely do not want your breakaway activated when a coupler has jumped the ball into the chain cradle! That is full 12V to those brakes and they will grab hard and you very likely will loose control of the TV and be seriously wrecked. I adjust my trailer brakes 1-2x a season and they will lock with my P3 at 3.4V with B1 boost! Anyway, this has happened, been investigated and documented well by states and the NHTSA, and there are owners even on two other forums who luckily lived through wrecks from this very reason because they didn't know better about proper setup.
You are to set up a ball tow trailer such that 1) chain length must be such that it will catch the coupler before hitting the pavement, 2) the electrical umbilical is of such length that it remains engaged with coupler in the chain cradle - this maintains your control and signaling to those on the road with you, and 3) breakaway is final defense when trailer leaves the TV and breakaway cable should not be attached to hitch anywhere, but separately off the frame.
Breakaway is a precise term, and you will find interpretation of the FMCSA applied: "Breakaway braking requirements for trailers. Every trailer required to be equipped with brakes shall have brakes which apply automatically and immediately upon breakaway from the towing vehicle. With the exception of trailers having three or more axles, all brakes with which the trailer is required to be equipped must be applied upon breakaway from the towing vehicle. The brakes must remain in the applied position for at least 15 minutes."
I have seen pole vaulted utilities three times in my years. I have seen complete breakaway twice. I personally dropped a carrier into the chains in the 80s with three 3 - wheelers on it after the coupler jaw dropped out after the nut and jam nut left! NOT FUN AND YOUR CORRECT MOVE IS TO BRAKE SLOW AND AS EVEN IN A STRAIGHT OF A LINE AS YOU CAN WITH THE TRAILER WAGGING BADLY. Don't hurry to the shoulder or make any sudden directional changes that will crash the trailer into you.