Early spark-gap tramsmitter manufactured by Eugene Ducretet between 1897 and 1904 for wireless telegraphy communication. Labeled parts are: "(O)" Spark gap mounted in box to muffle its noise, "(Bo)" Induction coil, "(I)" Interrupter for induction coil, "(M)" Oil-break telegraph key, "(P)" Antenna wire, "(T)" Ground wire "(i,i')" High voltage terminals of coil