The left side of the box is the 5 amp booster side. It has a 4 pin connector. The first set of two pins are for incoming AC power. Typically this is 15 volts AC / 5 amps from the 120 VAC transformer. The second set of two pins is track output this should also measure about 15 volts AC. Notice the small 4 wire jumper on the control bus jack which goes to the other side of the box. See below. The status light should be a solid red. a slow flash indicates a track short. A fast flash indicates the control bus signal is not present.
Here we see the right side of the box. This is the command station side. The other end of the control bus cable goes here and you also have the connection jack for the Cab Bus. Notice the 2 wire track output for a programming track. The track light is usually solid yellow except when in service mode programming /programming track mode. In Service mode the left side running the layout shuts off and the right side with the programming track output is now active.