Reginald Fessenden was dismissed from the National Electric Signaling Company in early 1911, and the legal battles that followed forced NESCO into receivership. However, the company continued in business on a limited basis, in this case supplying an alternator-transmitter -- a device originally developed by Fessenden -- for radio-telephony experiments.
The Electrical Experimenter, October, 1916, page 411:
NEW SYSTEM OF RADIO TELEPHONE
The radio engineer of today is still laboring on the important problem of transmitting speech without wires, and recently various systems have been developed, one of which was brought out through the research of Edward G. Gage, a well known radio investigator of New York City. His system has been thoroughly tested by the D.L.&W.R.R. at their Hoboken station, and the results obtained are more satisfactory than from other apparatus previously tested.
The high frequency alternator employed for producing the sustained waves is a modification of the Fessenden type. A remarkable feature of this machine is the fact that it runs at a tremendous speed of 40,000 R.P.M., just double the speed of the Fessenden or Alexanderson machines. The alternator used at Hoboken is driven by a 3-horsepower motor run by 150 storage batteries. This is done to secure constant speed regulation.
The control panel is illustrated in Fig. 1. At the right of the panel are two circular cases. In these the inductances are placed, controlled by a circular switch. The upper one is used as a secondary inductance, while the lower one is the primary. The amount of current which is radiated by the antenna is read on an ammeter, beside the inductance. The modulated current is controlled by a specially designed microphone placed in front of the panel. This microphone is provided with a water cooling system, so that if a large amount of current is to be controlled, water is sent through it to cool the microphone elements and their chamber. A special form of mouthpiece is employed to collect all the vibrations of the voice. At the left of the microphone can be seen the Fessenden electrolytic detector for receiving. A key, which is used for calling is mounted at the right of the microphone.
The novel transmitting circuit which is actually used in this new system is shown in Fig. 2. The high frequency alternator is connected directly in the antenna and ground circuit as indicated, and is shunted across a receiving coil C of a three coil transformer B. The second coil D, of this transformer is connected in series with a variable condenser VC, and an adjustable inductance I. The third coil E is linked to a telephone transmitter. This coil is wound over both of the other two coils CD. The principle involved is the modification of the antenna current by detuning.
In operation, when the telephone receivers are removed from the hook, the generator is automatically started, and thereafter no adjustments are necessary as long as the generator is run at a constant speed. A small button operates the change-over switch. From two or three amperes are usually radiated from the antenna.
The complete system has been employed in a series of tests by Mr. Gage, at a testing station on Long Island Sound. The National Electric Signaling Company cooperating in this work, with their apparatus on Fall River line steamers.
The use of the high frequency alternator makes it particularly applicable to railroad work, since it requires practically no adjustments. One objection is, of course, the expense of an outfit, but it is believed this can be reduced sufficiently to make it practical.