The Jersey City news. (Jersey City [N.J.]) 1889-1906, 1898-08-09
CARTY'S BRIDGING BELL
Features Of the Patent Sus-
tanned By Judge Buffing-
ton--An Important
Ruling.
[From the 'Electrical Engineer
I14Iv %

IFrom the aElectrical Engineer OF
July Isl
An important decision has just been
rendered in the T.. S. Circuit Court of the
Western District Of Pennsylvania by
Judge Burlington, sustaining the bridging
bell patent issued to j. j. Carly, No,
44s, los, of March 81, 1891. The litigation
for infringement was between the above
parties, and the defence was lack Of
novelty and of patentability. The decision
sustains the patent.
Prior to this patent it was customary to
connect the call bell magnets at the sew
eral stations in series in the main line
circuit together with q normally shunted
call sending generator and at each station
to provide a switch, which, when at rest,
maintained the continuity of the main
circuit through all the cell bell magnets
and kept the circuit Of the local trans
mitter battery open. When, however, the
switch was changed-which was done
when the receiver was taken from the
hook for use-it disconnected or short
circuited the bell magnet or generator
from the line and introduced in place
thereof the telephone transmitting and
receiving instruments and closed the
local battery circuit of the former.
1nOuSn this switch cHanSo at lue
two communicating stations removed the
bell magnet at such stations from the
| circuit. no such action took place at the
other stations. Consequently the voice
current had to traverse all the other mag
net h~elicest in the line and was much
weakened. not only by the resistance of
such magnets. but also by the counter
e-lectromotive forces or inductiye resist
ances developed in each. These were SO
active and energetic as to hinder CONVEX
sation. yet it was necessary that all bell
magnets should be connected with the cir
cuit. otherwise the several stations can
not signal each other. 1t will be noted
that in this system, which is called a
series-circuit, the component parts are 50
arranged that the current must pass
through all its parts, one after another.
1T is so styled in contradistinction to a
multiple circuit, which is one having two
or more of its parts so arranged That the
| current divides, portions Of It passing
through parallel paths afforded by the
| several parts. The two systems may be
thus illustrated: When incandeseent lights
are connected in multiple circuit, the cur
rent passes to one terminal OF eacn OF the
lamps which are connected to one side OF
a circuit and then divides UP, a portion
passing through each lamp to the other
side of the circuit, where all these pof-
tons are reunited Where such lamps are
connected in series, all the current must
flow into the terminal of the first lamp
and out of the other, and so on through
the successive lamps.
1t also appeared lQDCSS1DlG To ODld1u q
perfect inductive balance in a metallic
telephone circuit when the bell magnets
and telephone were connected IN series
and such inductive disturbances manifest
ed themselves generally in a~nnoyances
and sometimes were so intense as to pre-
won't conversation. Now it would seen.
that If, instead of the series circuit con-
nection for both call magnets and tele-
phones, a multiple circuit or bridging con-
nection after the manner of the simplest
form Of incandeseent lighting, was SUP
c4f+4,fS1 fhpc2 diffpI11fiRS NVQfIl1 he 1VOlu-
ed. but the conditions We're different SINCE
in a telephone circuit each station IS Dotn
a generating and utilizing one at the same
rents are likely to be short circuited by
the nearest bridge connection and thus
fail to reach the more distant statIoi-
which it is desired to signal. The addi-
tional fact that two diverse uses are to be
made of the current at the same station,
viz, signalling and transmission OF sound,
and that they are to be used Interchange
ably between all the stations, renders
necessary the addition Of other means and
factors to simple mere parallel afTange-
patentee suggested a simple and efficient
remedy.
The Carly patent shows and describes
a method of attaching telephone instru-
ments in multiple between the two sides
of a line. whether this line be a metallic
circuit or a grounded line. The call bells
are each permanently bridged etWee
the two sides of the line and are made
of high resistance and retardation. The
generator at each instrument is in a
| separate bridge circuit which is normally
| open. but closed when the generator is
| operated. The telephone apparatus
| proper is in a third bridge circuit. which,
like the generator circuit, is normally
| open. The telephone circuit of each IN
strument is automatically closed when the
| receiver is removed from its hook for use.
and this operation also closes q local
circuit containing the primary of the in
| duction coil, the local battery and the
transmitter In order that there shall
not be an undue leakage of the voice cur
| rents through the permanently bridged
call bell circuits, the magnets of these
cali bells are wound to a high resistance
| Casually a thousand ohms9 and are also
constructed in such a manner that they
will have a high co-efficient of self-ln-
| duetion. When a generator at any one
| station is operated it is connected across
the two sides of the line in parallel
with all of the call bell magnets on
the line. Part of the currents in this
| generator will, therefore. pass through
! each of the call bell magnets on the line,
thus causing them all to operate If the
| amount of the current generated is sufti-
Gent to accomplish this result. The sue
cessful operation of this system depends
on the fact that a coil possessing a hlgll
| eo-eficient of -self-induction will transmit
with comparative ease alternating or pull
sating currents Of low frequency, While /.
will form a practical barrier 50 similar
| The currents generated by the calling
| generator at any station are of sufficiently
low frequency to pass with comparative
| ease through the call bell magnets ar
| ranged along the line, while the rapidly
| alternating voice currents impressed upon
the line by the telephone apparatus at any
station will be compelled to pass over the
| main line to the receiving station without
being materially weakened by leakage
through the call bell magnets. At the re-
| ceiving station these voice currents will
| pass through the telephone receiver and
secondary coil Of the induction COLI these
being connected across the line at that
ctafion nv Virfiln nf fbP receiver being off
| it's hook. This path through the receiving
instrument is of comparatively low re-
%sistance and retardatfon and thus pfacti-
cally takes ali of the current from the dis
tant station.
Adopting this as a sufficient DESCRIPTION
of the device and its purDcse, the court
disnlisses as not pertinent a number OF
alleged anticipations, including patents of
Marley, Scribner and Van Rysselberghe.