Electrical World and Engineer, February 28, 1903, page 374:

A  Perambulating  Wireless  Telegraph  Plant.
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    One of the most ingenious and interesting innovations seen lately in the wireless telegraph field is the introduction of a perambulating plant by the American De Forest Wireless Telegraph Company, ostensibly for stock reporting purposes, though it serves equally well to advertise the company itself as an investment, to the enterprising financiers of the Wall Street district. On February 7 a decided sensation was made on the "curb" by the appearance of an electric automobile of special design bearing on one side the legend, American De Forest Wireless Telegraph Co. On another side was the statement, "Aerograms Received," and on still another side, "Approved and Adopted by the United States Government." The vehicle is surmounted by a glass showcase cupola about three feet square, and in front is a brass pole about twenty feet high, which serves in place of the usual antennæ wires. The operator sits inside the glass box, seen and seeing, so that all his operations can be watched by the "man in the street." Great interest was manifested in the novel machine, when it took up its position among the curb brokers and began to send the market reports into the offices of the Wall Street Journal and the nearby brokers.
    In equipping this automobile outfit it was not possible to use the full De Forest system as that would require a motor generator, and high-voltage transformer, which there was not sufficient space to accommodate; therefore, recourse was had to an induction coil giving a two-inch spark actuated by the storage battery furnishing power for the propulsion of the auto. The De Forest Company states that De Forest responders were placed in offices up and down Broad Street and successful aerograms giving the latest market reports were furnished to all simultaneously. It is understood that the company have a number of similar machines in course of construction and will rent them for the reporting of athletic events, and for the use of any one who wishes to leave the city and still keep in touch with his house or business.