Electrical Review, February 25, 1905, page 340:

Application  of  Wireless  Telegraphy  for  Domestic  Purposes.
TO THE EDITOR OF THE ELECTRICAL REVIEW:
    Noting a reference to an adaptation of wireless telegraphy to the operation of music boxes for entertaining purposes, mentioned in the ELECTRICAL  REVIEW of January 28, 1905, it occurs to me to call your attention to an application of wireless telegraphy to domestic purposes which may be of interest to your readers; as I believe it to be not only novel, but susceptible of extensive employment and with advantage in our homes.
    During the year 1904 and the present year as well I have used upon my dining-room table a tiny transmitter consisting of an induction coil with antenna, spark-gap and key, connected by means of a flexible silk cord with four small dry batteries under the table, these being used for sending Hertzian waves through the walls to the kitchen for summoning the maid. In the kitchen mounted upon a board was a second antenna, coherer, relay, electric bell (the tapper of which was used as a decoherer) and about eight small dry batteries. This outfit served to do away with the usual floor push-button which often wears holes in the floor carpet or rug and which button is so hard to locate especially if the table has been lengthened or moved and moreover necessitates making holes in floors and walls for running wires to the bell and batteries in the distant room, it also entails considerable expense, annoyance and dirt. The transmitter used is but little larger than a good sized paper-weight and is rather ornamental than otherwise. I arranged the antennæ in spiral form at the bottom so that by pulling them out and lengthening them I could use the transmitter under the same conditions from any room in the house, by the sick bed, for instance, for summoning the nurse or the maid.
    I recently had the pleasure of entertaining at dinner at my home my friends Dr. Lee De Forrest, of wireless telegraphy fame, and Mr. A. B. Freuzel, commissioner of rare minerals for the state of Colorado at the St. Louis Exposition, and they were much interested in the use of "wireless" at my table on that occasion, and Dr. De Forrest said he believed this to be the first application of the system to domestic needs. I might also state that nearly five years ago I used a somewhat similar outfit to ring my front door bell and fire a small cannon in my parlor while entertaining a party of friends at my home. On this occasion I carried the transmitter under my arm to the rear of the building while operating same. The wireless outfit which I employ might with advantage be modified for domestic use. It was built for me by Mr. W. J. Clarke, of the United States Electrical Company, of Mt. Vernon, N. Y., who has done some very early and interesting work in this field.
Yours very truly,               
WILLIAM  J.  HAMMER.    

    New York, February 7.