An Improved Telephonic Instrument, designed for Use on Poorly Insulated Lines, such as the Existing Wires of an Ordinary Wire Fence.
Year: 1895

page_text: Date of Application, 26th Aug., 1895-Accepted, 28th Sept.,
1895
COMPLETE SPECIFICATION.
An Improved Telephonic Instrument, designed for Use on Poorly
Insulated Lines, such as the Existing Wires of an Ordinary Wire
Fence.
We, GUSTAF DILLBERG, of Glen View Street, Paddington, Sydney, in the
Colony of New South Wales, Electrician, and PARNELL RABBIDGE, of Double
Bay, Sydney, aforesaid, Electrician, do hereby declare the nature of our invention
and in what manner the same is to be performed to be particularly described and
ascertained in and by the following statement :-
of
The object of this invention is to produce a simple and effective telephonic
instrument, whereby loud and satisfactory speaking may be obtained though the
line wire be exposed to serious leakage, in consequence
insulation.
This invention is intended for use on poorly insulated lines and on leads consisting
of one or more of the wires in ordinary wire fences.
poor
As it is both difficult and expensive to insulate such a wire from its ordinary
supporting fencing and straining posts, we purpose to construct the telephonic
instrument so as to be able to dispense with any insulation between the wire and
the posts, without impairing the satisfactory working of the circuit.
To accomplish this object we proceed as follows, and as shewn in the accom-
panying drawing in which: Y, Z represent two separate telephonic stations,
connected together by line wire L.
A and A¹ represent calling apparatus; B and B₁ batteries; E earth;
H and H rocking lever-switches and receiver-hooks; K and K' relay-armatures;
M, N, and M', N₁ coils of wire surrounding iron cores P and P'; R and
R receivers; T and T transmitters; a, b, c, e, and a¹, b, c, e¹, contact points;
d and d centres for H and H'; f and f¹ are press buttons connected to H and H¹
respectively.
The drawing represents the instruments whilst not in use.
When Y desires to
call Z, the button is pressed in contact with e, thereby bringing B into circuit,
the current passing through H, f, e, L, M' and N' to E, causing P₁ to attract K³,
bringing K into contact with c¹, thereby completing the circuit of Z from Bi
through d', a', A', K¹, e' to E and causing A' to ring.
When Z answers the call, he presses thereby ringing A notifying Y that he is
in attendance. When R and R¹ are lifted off H and H', the speaking circuit is
established through BabT MRL R' M' N¹ to E.
As B and B' are of
B and B are of equal strength and opposing each other.
equal strength and opposing each other, no battery current can pass from T
through M L M when L is perfectly insulated but must pass through N to E,
thereby inducing a current into M, inductively connecting the line circuit
namely:-M R L R¹ M'.
As the
When leakage ✗ occurs between L and E, the battery current traveis both
through M N, and M¹ N¹ in proportion to the relative resistances of M M¹
and N N to L and more or less through X to E according to the resistance of X.
The current passing through N, N is also varied by T and T₁ inducing a
current into M and M³, thus increasing the variations of the current in L.
resistance in T is increased the current passing through T¹ is proportionately
increased, and as the resistance in T is increased the current passing through T' is
proportionately increased, because Y is in shunt with Z through X; thus the
variations in T are registered in R and R', and the variations in T are registered
in R' and R.