Dr. Branly's latest apparatus, which allows of controlling different kinds of mechanical effects at a distance, has awakened great interest owing to the applications which it is likely to receive in practice. The apparatus enables an operator in a distant station to control by means of radio-telegraphy the lighting of lamps, explosions of mines, sending up rockets, mechanical movements such as the boring of metals, and any kind of action which is brought about by electro-magnets. Steering of torpedoes is one of the interesting uses of Prof. Branly's system, and other uses in military operations are at once apparent. The principle of the system lies in the use of a series of distributing disks placed on a shaft which is driven by an electric motor. Suppose the operator wishes to light electric lamps at the distant point. In the lamp circuit is a relay which opens or closes it. This relay is worked from the circuit of a coherer and sensitive relay, so that when the operator sends a wave signal the coherer responds, closing the first circuit as in radio-telegraphy. This causes the lamp relay to operate and the lamps are lighted. What is now desired is to have the operator control a number of such apparatus at a distance. For this purpose each apparatus (supposing there are four of them such as he uses in his laboratory for demonstration, namely, a set of incandescent lamps, a revolver which is fired by an electro-magnet, an electric fan and an electromagnet lifting a cannon ball) uses a separate disk placed on the shaft, with a fifth disk for controlling the motor. Each disk carries a projecting sector which makes contact with a brush during one-fifth of a revolution. During this period he can send sparks to operate this particular apparatus, and no other. One of the principal features of the system is what Prof. Branly calls the "automatic telegraph." It serves to show the operator at the sending post the proper moment for sending the signals for controlling* the different effects. These check signals are given him by a radio-telegram which is received upon a band of paper from a Morse receiver placed at the sending post. An apparatus placed at the receiving station sends these signals at the proper time by means of a spark coil connected so as to operate at certain periods by a special revolving disk. The latter is mounted upon the same shaft which carries the other disks. On the automatic telegraph disk are five groups of teeth, and each group gives an appropriate set of sparks so as to form a signal. A complete revolution of the disk thus sends five signals to the sending post to be recorded upon the paper, and these signals occur at equal intervals, or one-fifth revolution, corresponding to about four inches on the paper strip. On the upper band of this paper strip there are five signals, formed of from one to five dots. Suppose that there are four working disks on the shaftj 479 which respectively operate (1) the firing of a revolver, (2) the air fan, (3) lighting of lamps, (4) lifting of an iron ball. The contact projections on these disks are such that (1) is in contact during the period between the first and second signal on the strip, (2) between the second and third, and so on. By sending a spark while the paper is passing between the first and second signals he can control the working of circuit (1), and in the other intervals he operates the remaining circuits. Here the same coherer is used for all the different circuits at the receiving end, and it is in-close'd in a metal box screened by wire gauze so as to preserve it from the action of the automatic telegraph spark. At the sending station the coherer of the Morse receiver is also placed in a protecting box so as to protect it from the sparks of the coil. The same mast is used in turn for the different operations at the sending and receiving stations. The electric motor which drives the shaft at the receiving station is also controlled by a relay and coherer in the same way as the other devices. It has a special disk on the shaft allotted to it, which makes its contact during the last period or between the fifth and first signals of the automatic telegraph. At this time the operator can start or stop the motor. Another set of check signals is used which enables the operator to see whether the desired effect has been actually produced so that he can note accurately whether a certain mechanism which he set working is still continuing to run. The main shaft at the receiving station carries a separate set of disks which are used especially for this check system. Taking the case of the lamp lighting circuit, for instance, the disk belonging to it carries a projecting tooth which makes contact with a brush once in each revolution of the shaft, and can thus complete a circuit which includes the spark coil of the automatic telegraph. This action causes a signal to be sent to the operating station which is recorded on the paper strip. Placed in the lamp lighting circuit is a special relay which comes into action when the lamps are lighted. This relay keeps the above-mentioned check signal circuit prepared so that when the contact tooth comes around it will complete the circuit. But should the lamps have failed to light the relay would remain open and no signal could be sent. The operator would thus see that the circuit had failed to work. As regards the position of these signals on the paper strip, they are recorded just beside the regular signals of the automatic tele-graph by means of a dash of a certain length w h i ch perforates the second signaling band. To check up the working of the apparatus at any time the operator first starts up the motor by a wave signal and then re-ceives the series of dashes which the automatic telegraph sends him and which can be observed on the paper strip. He then stops the motor, and can repeat this operation at any time. In operating a system of this kind, one of the essential points is to have it protected against the action of accidental sparks, atmospheric effects, etc., and Prof. Branly has found an effective means for doing this, outside the syntonizing of the apparatus, which at present is difficult to carry out. Naturally in the case of a continuous succession of sparks which are sent with the object of creating confusion it is impossible to work any radio-telegraphic apparatus, but the present method answers very well for accidental effects. A special interrupter is placed in the circuit of the receiving station. It consists of a wheel rotated by a motor, having a set of say five narrow contacts upon it, with two brushes placed side by side so as to close a circuit. The shaft carries a cam which the wheel can draw along with it in its rotation and the cam operates a closing key for the work circuit. A spark from the sending station causes the motor to turn by means of a coherer and relay, after which the circuit is opened by the wheel's revolution, since the first contact has now left the brushes. If at the moment the second contact touches the brushes a second spark is not sent, a lock bolt stops the wheel and motor and by a special electric device the cam which made one-fifth turn is suddenly brought back to the zero point. Should, however, a spark occur at the right moment the cam is allowed to go along with the wheel, and by sending the other sparks at each contact the cam makes a whole revolution and is now able to trip up the key and make 480 contact for the work circuit. As it takes five properly-spaced sparks to operate the whole movement, it is seen that an accidental effect could hardly have any effect on the apparatus. In practice the operator sends a rapid succession of sparks in the period shown by the automatic telegraph, and these last for twenty seconds for each operation or for closing one work circuit. Thus he gives an action at each one of the five points mentioned above and the key is accordingly closed for that special circuit.
This article was originally published with the title "Dr. Branly's Apparatus for Control of Distant Mechanical Effects"