Multiplex Telephony and Telegraphy by Means of Electric Waves Guided by Wires (Google eBook)

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U.S. Government Printing Office, 1919 - Telephone - 102 pages
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Page 78 - Statutes, when such invention is used or to be used in the public service, without the payment of any fee: Provided, That the applicant in his application shall state that the invention described therein, if patented, may be used by the government or any of its officers or employees in the prosecution of work for the government, or by any other person in the United States, without the payment to him of any royalty thereon, which stipulation shall be included in the patent.
Page 24 - F' the detector D is operatively connected; E is the earth connection. The local battery telephone sets are connected across the two line •wires in the usual manner. In both sets 1 is the microphone transmitter; 2 is the local battery; 3 is the induction coil; 4 is the ringing system, including the bell and hand generator; 5 is the switch hook; 6 is the telephone receiver. It was found that cross-talk was heard in the...
Page 31 - C' and L', and at the receiving end the oscillation transformer R in the secondary circuit of which are included the usual tuning elements and operatively connected to them the detector and its telephone as a means of receiving the signals. As noted in the case of the preliminary local circuit tests, it was found that over this particular line it was not necessary to use a FKJ.
Page 28 - The transmitters first tried were those of the microphone type inserted in the armature circuit of the dynamo and provided with water cooling when currents of several amperes were to be used. It was soon found, however, that the efficiency of transmission of this cable line was so good for electric waves of these frequencies that a very small current, in the neighborhood of 2 milliamperes, sent into the line was amply sufficient for good speech at the receiving end about 7 miles distant. No attempt...
Page 20 - FIG. 1. j- , i . j disturbances found under city conditions, but the metallic circuit could be reduced to silence again by introducing in the ground connections the necessary tuning elements of magnitudes suited to wireless telegraphy. Next, the twisted-pair telephone line was equipped with a complete standard local battery telephone set, as installed for commercial practice, with the exception that the local battery circuit of the transmitter telephone set was opened and a few...
Page 14 - ... conductor, is as follows : Laboratory to main exchange, underground cable, No. 22 B. & S. Main exchange to west exchange, underground cable, No. 19 B. & S. West exchange to Cleveland exchange, underground cable, No. 19 B. & S. Cleveland exchange to Bureau of Standards, underground cable, No. 19 B. & S. All underground cable except from Bureau of Standards to Wisconsin Avenue and Pierce Mill Road, about 3,400 feet, which is aerial cable. This line is equipped with protective heat coils of a standard...
Page 13 - ... 5.4 ohms at 100,000 cycles. This would require a capacity of about 0.3 microfarad for resonance at this frequency, but in the experiments conducted at 100,000 cycles it was found necessary to decrease this amount on account of the fixed auxiliary inductance of the leads. CONSTANTS OF THE TELEPHONE LINE. The telephone line Used in these experiments extends from the Signal Corps laboratory at 1710 Pennsylvania Avenue to the Signal Corps research laboratory at the Bureau of Standards. This line...
Page 28 - A circuit was next made up with high-frequency apparatus inserted directly in the line in series, instead of in the bridging arrangement shown in figure 5. The circuit used is shown diagrammatically in figure 7, in which L and L' are the secondary coils of the transmitter and receiver, respectively.
Page 13 - The machine is intended to be used with a condenser, the capacity reactance of which balances the armature inductance reactance which is 5.4 ohms at 100,000 cycles. This would require a capacity of about 0.3 microfarad for resonance at this frequency, but in the experiments conducted at 100,000 cycles it was found necessary to decrease this amount on account of the fixed auxiliary inductance of the leads. CONSTANTS OF THE TELEPHONE LINE The telephone line used in these experiments extends from the...
Page 23 - Simple experiments proved the efficiency of this arrangement, and when the metallic telephone circuit, equipped with a standard local battery set, was connected to earth in the manner described, the operation of the battery set was perfectly quiet and equally good with and without such earth connections. The point was now reached where the road was clear for duplex telephony, and for this purpose the apparatus and methods employed in wireless telephony were applied to one of the wires of the metallic...

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