Gene,
I can't name the brand but it looks familiar, It is the cheapest and most basic of brake controllers, a crude time-ramp brake controller.
When the service brake pedal is depressed a signal from the stoplight switch activates the trailer brakes and over a small period of time, probably something like 30 seconds, the brake controller "ramps" up trailer braking from minimum to maximum. If the driver is using the brakes for a long gentle deceleration and if the trailer brakes are adjusted up fairly tightly he will have to release and reapply the brakes several times in order to prevent the brake controller from locking up the trailer brakes.
That controller will make a good paper weight. Throw it away and buy a good one that applies trailer brakes in proportion to pressure applied to the truck brake pedal.