Improvements in Testing and Protecting Apparatus used in conjunction with Telephone, Telegraph, or other Electrical Circuits.
Year: 1898

page_text: Date of Application, 28th Apr., 1898-Accepted, 6th Aug.,
1898
COMPLETE SPECIFICATION.
Improvements in Testing and Protecting Apparatus used in
conjunction with Telephone, Telegraph, or other Electrical
Circuits.
We, DANIEL SINCLAIR, Engineer-in-Chief, and WILLIAM AITKEN, Engineer_to
National Telephone Co., Limited, of Oxford Court, Cannon Street, in the
City of London, 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:--
This invention relates to improvements in test board apparatus used in con-
nection with telephone, telegraph or other systems where large numbers of
wires have to be conveniently arranged for testing and cross-connecting or
re-arranging; and for providing on such apparatus efficient protection from
lightning, or currents from electric lighting, traction power or other systems
that would detrimentally affect the apparatus in telephone, telegraph or other
switch-rooms, and has for its objects the improvement of the apparatus, the
reduction of the number of parts, and the simplification of the arrangements
at present in use for this purpose and the attainment of better results.
In test-boards at present in use the following imperfections exist:-(1) The
test-jacks are either exposed altogether or covered-in by sliding or hinged doors
which have practically to he always kept open for testing purposes, also the
construction of the test-jacks does not lend itself to a dust-proof arrangement
of the apparatus.
(2) The cable-heads or terminal boards have simply points or terminals on
which to end the cables or leading-in wires and to which the connecting wires
to the test-jacks or apparatus may be joined, without any facilities for protecting
the apparatus from lightning or other currents; or, an imperfect form of light-
ning arrester only is attached to the cable head terminals.
(3) Where lightning arresters and fuse coils for protecting the apparatus from
lightning and other currents have been provided, they have usually been fitted
separate from the test-jacks or cable heads rendering it necessary for wire con-
nections to be formed between the cable head terminals and the arresters and
fuses and between the latter and the test-jacks.
The object of our invention is attained by the following means:-
Firstly. By the use of test-jacks constructed in such a manner that dust is
not admitted to the contacts.
Secondly. By the use of carbon lightning arresters and fuse coils in combina-
tion with the cable heads.
The invention is illustrated by the accompanying drawings.
Fig. 1 is a diagrammatic representation of the circuit through a test-jack
a lightning arrester and a fuse coil on the cable head.
Fig. 2 is a front elevation of a part of two strips of test-jacks.
Fig. 3 is a section of two strips of test-jacks.
Fig. 4 is a side elevation of a part of a strip of test-jacks..

page_text: Fig. 5 is a section of a test-plug used in conjunction with the test jacks.
Fig. 6 is a front elevation of a 102 pair cable-head fitted partly with lightning
arresters and fuse coils.
Fig. 7 is a longitudinal section of same.
Fig. 8 is a transverse section of same.
Fig. 9. shows alarm fitted to indicate when a fuse has gone.
Similar parts are indicated by similar letters and figures on the various
drawings.
a
Fig. 1 shows the simple arrangement of the apparatus according to our inven-
tion. The wires from the switchboard apparatus to be protected end on springs
and of the test-jack. The cross-connecting wires are attached to the two
opposite springs al and 1 of the test-jack and to the springs in connection
with one side of the fuse coils a² and 62. The path of the working current is
then through the fuse coils f and f¹ to the line springs a³ and 63 to which
the cable or leading in wires are to be soldered.
Figures 2, 3 and 4 illustrate the test-jacks. These are preferably constructed
on the principle of the spring jacks described in our Patent Specification
No. 26968, dated 27th November 1896, i.e. with shouldered springs in rectangular
holes in the back strips of vulcanite which springs are separated and held rigidly
in position by wedges of vulcanite or other suitable material, so that no screws
or colleted springs are necessary for fixing. The two pairs of springs a and a
and and respectively make contact. The a and b springs of each pair
have a small piece of half round platinum or other suitable wire affixed centrally
in the line of the springs at the points where they make contact and the ¹ and
springs have a strip of similar wire at right angles to that previously specified
so that there is a good point contact where the two pieces of wire cross.
contact is cleaned each time the plug is inserted. The soldering tabs of
springs a a, b and b' are prolonged behind and twisted so as to form a space c
for the switchboard cable between them and the iron plate d, the cable being
lashed to the iron plate d by tape or other suitable material passed through
holes and and the like.
This
To prevent the long tabs making contact with each other, each is rivetted to
a strip of vulcanite, as shown at e. The front strip g may be formed of vulcanite,
wood or other suitable material, and is pierced with as many rectangular holes
as there are sets of springs. Behind each hole is a small metal shutter h which
normally closes it, the coiled spring holding the shutter firmly in position but
allowing the plug to enter when necessary, and automatically closing the hole
when the plug is withdrawn.
These shutters effectively prevent dust from entering by the jack holes. The
front and back strips and are firmly mounted on an iron plate d and are
made slightly shorter than the iron plate so as to allow it to ride in slots formed
in shelves at top and bottom. The iron plate and front and back strips may
however, be made of equal lengths and be fastened by jack fasteners or screws
in the well known manner. The front strip g and back strip are also made
of equal thickness so that when two or more strips of jacks are in position as
shown in Fig. 3, there is no way by which dust can enter.
Fig. 5 represents the plug used in conjunction with the above described test-
jacks and such plug may be constructed in any of the well known ways.
In Figs. 6, 7 & 8 which illustrate a cable head in conjunction with lightning
arresters and fuse coils constructed according to our invention, n represents a
rectangular cast iron box or cable head, the back, sides and ends being con-
structed in the well known manner, the front, however, being formed with a
sufficient number of openings Z which number will vary according to the number
of wires in the cable for which the head is required. Preferably we make each
opening sufficient to accommodate 10 or 11 metallic circuit lines and as the
head illustrated is for a 102 pair cable it has eight openings for 10 metallic circuits
and two for eleven.

page_text: The metal forming these openings is channelled or grooved as shown at O
Figures 7 and 8.
Preferably we use carbon lightning arresters and fuse coils of the well known
pattern. E being a strip of brass or other suitable metal forming the earth
plate, connected to the front of the cable head as shown at E and E¹, the cable
head being connected to earth. p and p¹ etc. are carbon blocks which, with a strip
of perforated mica or other suitable material between form the lightning arrester.
p and p2 are in contact with the earth plate, and the line springs a³ and b³
rest in a groove in p and 23 respectively. Springs a² and a3 and 63 and 63 have
between them (readily removable for repairing purposes) fuse coils f and fl.
These consist of a small coil of wire, connected at one end to the frame which
makes contact with springs a³ or 63 and at the other end to a small cavity filled
with metal which fuses at a low temperature. Into this cavity is inserted a pin
whose head is carried by springs a² or 63 which is normally in tension. When,
therefore, a current of sufficient heating power passes through this coil the
fusible metal melts and allows the spring a2 or 2 to withdraw the pin thereby
breaking the circuit and preventing the current from injuring the switch-room
or other apparatus.
The springs a and 62 have a piece nearly stamped out which is curved forward
and formed into a soldering tab as at a² and 62 or they may be thickened and
have screws inserted, the cross connecting wire then being clamped by the head
of the screw as shewn at a¹.
Rings are screwed into the castings and are for carrying the cross-connecting
wires.
The springs a a³ 62 and 63 are to be fixed in position as follows:-The springs
which have spaces
are temporarily held in position by wood or metal pieces
cut for them, another piece q at each end crossing and being held in position
by screws 2. The springs are kept from moving backward or forward by pins q³
which pass through the pieces g and through a hole in the spring stamped for
the purpose. The cable head is then placed on its face and plaster of Paris
or other suitable compound is forced between the springs thus forming a slab of
sufficient thickness to withstand the pressure it may afterwards be subjected to.
After this material has set, the pieces 7 &c. are removed and the adhesive
material is saturated with paraffin wax to increase its insulating properties.
Figure 9 illustrates an arrangement for indicating to an attendant that one
of the fuses has gone. s and are two continuous strips of metal mounted on
a strip of vulcanite which runs from end to end of the cable head and carried
by brackets. The strip has a series of light springs in line with each fuse
coil, spring a3 or 62 and the like. When the spring 62 is released by the fuse
melting, it causes the corresponding light spring on t to make contact with the
strips thus closing a local circuit in which is the indicator and battery w¹.
The shutter of indicator falls and closes another local circuit in which is the
bell and battery, the bell therefore rings.
One or more indicators may be fitted for each cable head, and one bell may
be common to a group of cable heads.
Although we prefer to fix the springs into the cable head by means of adhesive
material, we do not limit ourselves to the method, as they might be fixed in the
following manner. Four vulcanite bushes might be inserted in the cast iron
front for each metallic circuit and four metal screws with suitable heads inserted
in them, the a² a³ 62 and 63 springs then being attached to the heads of these
screws.
Also we do not limit ourselves as to the application of this invention.
Although principally useful for test-boards, the cable heads constructed according
to our invention may be affixed to the cables at the ends furthest from the
5 exchange or switch room, such as a cable hut or terminal pole, and similarly
our test jacks may be used for pole test boxes on overhead wire routes where
it is necessary to divide the line into sections for testing purposes. They may

page_text: also be used for telegraphs and police or fire alarms or other kindred service
where spring jacks are required in exposed positions.
This invention admits of other modifications in the arrangements which would
readily suggest themselves to those skilled in the art. We therefore do no
limit ourselves to the precise arrangements shown or described herein.
Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed we declare that what
we claim is:-
-
1. The combination and arrangement of parts forming test boards, and com-
prising the necessary apparatus for joining the line wire to the inside or
switchboard wire, facilities for testing the same, and apparatus for protecting
the switchboard parts from lightning or other injurious electric currents, sub-
stantially as described and illustrated in the accompanying drawings.
2. A test jack constructed substantially as described and illustrated in the
accompanying drawings.
3. The combination of a test jack or any other pattern of spring. jack with
a spring shutter closing automatically with the object of keeping dust or other
foreign matter from the contacts substantially as described.
4. The combination of a cable head and carbon lightning arresters and fuse
coils, substantially as described.
5. The fixing of springs in a cable head for the purpose of carrying carbon
or other lightning arresters and fuse coils, or one or both by compartments or
openings in the front of the cable head filled in with an adhesive material or
mixture, substantially as described and illustrated in the accompanying drawings.
6. The combination of a cable head and carbon, or other lightning arresters
and fuse coils with a local circuit having an indicator to show on what cable
head a fuse had gone and a bell common to a number of indicators to give the
alarm, substantially as described and illustrated in the accompanying drawings.
Dated this 27th day of April 1898.