Improvements in Long Distance Telephony.
Year: 1889

page_text: Date of Application, 21st Jan., 1889-Accepted, 2nd Nov., 1889
COMPLETE SPECIFICATION.
Improvements in Long Distance Telephony.
I EUGENE GWOSDEFF of 39, Znamenskaya Street, St. Petersburg in the Empire of
Russia, Gentleman, do hereby declare the nature of this invention and in what
manner the same is to be performed, to be particularly described and ascertained
in and by the following statement:-
Difficulties have hitherto been experienced in telephoning at long distances, and the
object of this invention is to overcome these difficulties.
I have found that in order to obtain a perfect working of microphones and of
telephones (of any construction) at long distances, it is only necessary to realise the
following conditions: (1) There should not be intercalcated at any point in the
telephone line, any electro magnet; (2) The extremities of the line should be insulated
from earth; and (3) The microphones and telephones should be connected to the line
through condensers.
In the accompanying drawing, I have illustrated my invention by diagrams which
will be particularly referred to hereafter.
I represents telephonic wires, T telephones, K K¹ condensers, B batteries, and
E earth (see Fig. 1).
The capacities of the condensers should differ, that is to say, the capacity of the
microphone condenser, K, will depend upon the force of the current from the battery
and tho length of the line, as well as the sum of the capacity of all the receivers inter-
calcated in the line.
The telephonic condenser, K¹, on the contrary, should have a small electric capacity,
so as not to augment uselessly the capacity of the line; in fact, this condenser
can be reduced, in certain cases, to two sheets of metal movable the one on the
other.
When using the telephone, it is indispensable to exclude or cut out from the circuit
the microphonic condensers when one listens, but it is necessary, on the contrary, to
interpose the microphonic condenser. in the circuit when one speaks.
These arrangements provide for the possibility of using the telephone for distances
of many hundreds of kilo-metres.
The telluric, terrestrial, and thermo-electric currents do not, owing to the arrange-
ment above indicated, produce any detrimental influence on the line.
When the line is composed of two wires without earth connection, as indicated at
Fig. 2, 1 neutralise the effects of induction by connecting the telephone, T, to cach
line L and L, through condensers K' and K₁, the capacity of which is in accordanco
with the resistance of the corresponding line.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is
The improvements in long distance telephony herein described, consisting in the
use of
=
1. A direct line without any intermediate electro magnets.
2. A line the extremities of which are insulated from earth.
3. The microphones and the telephones connected through separate condensers to
the line and with the earth, or to a return line, in this latter case by means of con-
densers, the electric capacity of which is in accordance with the respective resistances
of the two lines.
Dated this 21st day of Jannarv 1889