Think of it this way: if you're driving a car with an automatic transmission, the car will automatically shift the transmission for you as the speed increases or decreases. In a diesel-electric locomotive, this shifting process, which is electrical, is called "transition," specifically "forward transition" as the speed increases and "backward transition" as the speed decreases.

In road locomotives built since the mid-1950's, transition is made automatically, without any action required by the operator.

Early diesel-electrics did not have automatic transition, thus the operator was required to manually operate the Transition Lever (it's shown in the center of your photograph) at the required times.

As diesel-electric locomotives developed, Automatic Transition became standard. If any unit in the locomotive consist was not equipped with it (whether automatic Foreword Transition, automatic Backward Transition, or both), the operator was required to manually "shift" the Transition Lever. The badge you see informs the operator of this.