Improvements in Phonoporic Telegraphy.
Year: 1891

page_text: Date of Application, 14th Apr., 1891
Complete Specification Left, 13th Jan., 1892-Accepted, 13th Feb., 1892
PROVISIONAL SPECIFICATION.
Improvements in Phonoporic Telegraphy.
I, CHARLES LANGDON-DAVIES, of Faraday House, Charing Cross Road
London, Electrician, do hereby declare the nature of this invention to be as
follows:-
In phonoporic telegraphy I have heretofore employed a transmitter in which
there is an iron core surrounded by multiple windings.
One of the windings is connected at one end through a receiving instrument with
the line wire. A second winding is connected by one end to earth. The other
ends. of these windings are insulated so that there is no through circuit. Again
another winding (or windings) forms part of a local circuit in which a key is
included and also a battery and a vibrating circuit closer.
When the key is
depressed the vibrating circuit closer is kept in motion by the intermittent
attraction of the core; it vibrates in front of the core, opening and closing the
local circuit. So, induced currents or impulses are caused to pass along the line
wire. Now in such transmitters as heretofore made this key circuit has been open
except when the key is depressed. I have found however that the reception of the
signals is much improved by the closing of this local circuit and I so construct the
key that when it rises and leaves the battery contact stud it comes upon another
contact stud, thereby closing a circuit through the core winding but in such a
manner that the vibrating circuit closer ceases to be operative.
Dated this 13th day of April 1891.
C. LANGDON-DAVIES.
COMPLETE
SPECIFICATION.
Improvements in Phonoporic Telegraphy.
I, CHARLES LANGDON-DAVIES of Faraday House, Charing Cross Road,
London, Electrician, 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:-
In phonoporic telegraphy I have heretofore employed a transmitter in which
there is an iron core surrounded by multiple windings.
One of the windings is connected at one end through a receiving instrument with
the lin wire. A second winding is connected by one end to carth. The other
ends of these windings are insulated so that there is no through circuit. Again
another winding (or windings) forms part of a local circuit in which a key is
included and also a battery and a vibrating circuit closer. When the key is
depressed the vibrating circuit closer is kept in motion by the intermittent
attraction of the core it vibrates in front of the core, opening and closing the
local circuit. So, induced currents or impulses are caused to pass along the line
wire. Now in such transmitters as heretofore made this key circuit has been open
except when the key is depressed. I have found however that the reception of the
siguals is much improved by the closing of this local circuit and I so construct the
key that when it rises and leaves the battery contact stud, it comes upon another
contact stud, thereby closing a circuit through the core winding but in such a
manner that the vibrating circuit closer ceases to be operative.
The diagram annexed represents schematically a transmitter and receiver.
P is the phonoporie secondary of multiple wire it is wound around the iron

page_text: core N. One wire is connected to earth wire at E and the other wire to the line
coils R of the receiver and through the receiver to the line at L.
This receiver is worked by impulses arriving from a distant transmitter and,
when receiving the transmitter, shewn in the diagram, serves to connect the receiver
with the earth or return wire.
Cis the primary coil having a resistance of say 100 ohms and also wound upon
the core N. One end of the coil is connected at D to the bridge of an ordinary
key K. The other end of the coil is connected to the spring armature A which
when at rest is in contact with the spring V. G is a screw stop and B is a battery
connected with V and with the front contact of the key K.
These arrangements so far do not differ in any important way from what has
been usual in phonopore transmitters since phonoporic telegraphy was invented
by me.
When the key is put down the core N is magnetised and the armature A vibrates
rapidly at a regular speed opening and closing the battery circuit and electric
impulses pass in the line wire.
When the key K is not in use the circuit through the multiple coil Chas
heretofore remained open. I now arrange that the key when in its position of rest
shall connect the opposite ends of the coil C. For this purpose establish a
connection W between the end of the coil (and a circuit closer such as the back
contact of the key K so that when the path through the armature A spring G
and battery B is interrupted by the key another path avoiding these parts is
provided.
The result of closing the circuit through C is to greatly increase the action on
the receiver of the impulses arriving from the distant station.
Instead of the ordinary fixed back stop of the key, I sometimes use a pin switch,
or any other convenient arrangement, for making the necessary commutation.
The key may if desired be so arranged as to cut out the receiver when it is
depressed.
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 arrangement of a phonopore transmitter in such manner that the circuit of its
primary coils is complete when the key is not in use to connect the transmitting
battery therewith.
Dated this 20th dow of December 1801
C. LANGDON-DAVIES.