Improvements in Multiplex Telegraphy.
Year: 1897

page_text: Date of Application, 2nd Jan., 1897-Accepted, 13th Feb., 1897
COMPLETE SPECIFICATION.
Improvements in Multiplex Telegraphy.
1, JAMES MARK BARR, of Castle House, Shooter's Hill, in the County of
Kent, Electrical Engineer, 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:-
It has been proposed to effect multiplex telegraphy by connecting a number-of-
different stations or instruments by a single line conveying alternating or inter-
mittent.electric currents, providing each pair of correlated stations or instruments
with a condenser and self induction coil adjusted to a different periodicity, so that
of all the receiving instruments connected to the line only that which is connected
to it through a condenser and self induction coil adjusted to a special periodicity.
receives signals transmitted by currents of that special periodicity.
This is founded on the well known principle that if I represent the self induction
and the condenser capacity, these may be so selected that when their product k;
is suitably related to the periodicity, there is electrical resonance, that is to say,
a transmitting and a receiving instrument connected through a self induction coil.
and a condenser giving the product lk, will respond to one another, when the
periodicity is that to which Ik is suited, but will not respond when there is any,
other periodicity, unless the product 1k be changed to suit that other periodicity.
My invention relates to means of effecting multiplex telegraphy on a similar
principle, but so modified that currents of one and the same periodicity serve for
operating all the instruments, yet in such a way that only one of a number of
receiving instruments shall respond to that one of a number of transmitting
instruments which is duly correlated to it in respect of self induction and capacity..
For this purpose, having determined in a known manner the self induction and
condenser capacity such that their product 1k is that required to produce electrical
resonance with a given periodicity. I make up this product by placing a self,
induction coil of certain value and a condenser of certain capacity at one station or,
instrument and a self induction coil of another value and a condenser of another
capacity at the correlated station or instrument selecting those values in such a
way that their combined effect at the two stations is to give electrical resonance.
I do not however make these values equal but employ values different for each
pair of correlated stations or instruments determining them on the following known
grounds.
If, and, express the self inductions at the two correlated stations, their com-
bined effect as a factor is 1, +l, and if k₁ and k, express the capacities at the two
1
stations their combined effect as a factor is
+
-
k₁
k₂
1
k₁ ky
k₁ + k₂'
and the com-
k,
bined effect of the self inductions and capacities, as a whole. is (2₁ + %)
k₁
K1 Kg
If this be equal to 1k, the product required for electric resonance with the given
periodicity, then if the values of l₁, la, k₁, k₂, for one pair of correlated stations or
K1 Kg
If this be equal to 1k, the product required for electric resonance with the given
periodicity, then if the values of h₁, l₂, k₁, k, for one pair of correlated stations or
instruments such as A A₁ differ from their values for another pair of correlated
stations or instruments such as B, B₁ although A can communicate with A₁, it
[Price Ed.

page_text: cannot communicate with B, and although B can communicate with B₁ it cannot
communicate with A₁. Let it be assumed for instance that the values for A are
as above and k₁, that for A, they are l₂ and k₂, that for B they are l, and k
and for B₁ they are 4 and k these latter values being such that ( + 1)
k's k
kg + ka
-
:lk then although A and A, can communicate and B and B₁ can also
communicate, A cannot communicate with B, nor can B communicate with A, because
in the one case the combined effect of self induction and capacity is (4+1)
k₁
and in the other case it is (4, + 12)
:
'k3
k₂
ks + kg
tok the value required for resonance.
ka
k₁ + k
neither of which quantities is equal
It is to be understood that any values whatever including zero may be given.to
the terms and k in each case provided they are such that their combined effect
shall always be that suited to the periodicity to give electric resonance.
Consequently it is not necessary that both correlated stations should have both
a self induction coil and a condenser, one of the stations may have both of these,
the other having neither, or one of the stations may have the self induction coil
and the other the condenser. The transmitting and receiving instruments may be
of any known kind operated by the rise of current due to electric resonance.
When the line has branches, no electric generators are required, except at one
main station causing the line to be continually traversed by currents of the required
periodicity, so that the operator at any station has only to use one or other of his
transmitting instruments in order to communicate with that receiving instrument
at another station which is correlated as described with the transmitting instrument
employed.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed I declare that what I
claim is:-
The herein described method of effecting multiplex telegraphy in one line
traversed by alternating or intermittent electric currents of certain periodicity and
having transmitting and receiving instruments connected to it through condensers
and self induction coils, the condenser capacity and self induction being different in
quantity for each instrument but such that the combined effect of these for each
correlated pair consisting of a transmitter and a receiver is that suited to the
periodicity for giving electric resonance.
Dated this 2nd day of January 1897.
ABEL & IMRAY,
Agents for the Applicant.