This application discloses a method implemented of recognizing a keyword in a speech that includes a sequence of audio frames further including a current frame and a subsequent frame. The system is incorporated within an enclosure, which is transportable, such as on a vehicle trailer. The amount of charge in the vehicle battery is controlled in such a way that the state of charge of the battery at least does not fall below the lower state-of-charge limit. Charges might be assessed to the advertiser, perhaps subject to one or more conditions being met. The system further comprises a ventilation conduit extending between the bowl and drain.