English: First experimental radiotelephone system on a US Navy ship, built by American engineer Lee De Forest in 1907. One of the earliest AM (voice) radio systems, 26 units were installed on the ships of the "Great White Fleet" and tested on their well-publicized around-the-world cruise in 1908. This picture is of the unit installed on the bridge of the flagship, USS Connecticut. It consisted of a 40 kHz transmitter (left) using a variation of the Poulsen arc oscillator, and a receiver (right) using De Forest's Audion vacuum tube as a detector. The set had a limited range of about 5 miles. The transmitter uses an oscillator consisting of a 220V arc between copper and carbon electrodes in the flame of a small alcohol lamp (visible on R side of unit) attached to a resonant circuit consisting of a coil of wire and capacitor in series. The negative resistance of the arc excites resonant oscillations in the tuned circuit. The antenna is attached to an output coil inductively coupled to the first coil. The carbon microphone visible on the front of the unit is connected directly in the ground wire of the transmitter. However the Navy evaluated these devices as a failure, and they were scrapped after the cruise. Information from . Herbert T. Wade, "Wireless Telephony for the Navy", Telephony magazine, May 1908, p. 365-367.
Caption of picture: THE FIRST SET OF WIRELESS TELEPHONE INSTRUMENTS FOR THE UNITED STATES NAVY. INSTALLED ON THE FLAGSHIP USS CONNECTICUT.