LECTRICA
Year: 1898

page_text: Date of Application, 26th Mar., 1898 -Accepted, 25th Mar., 1899
A communication from THE ANTWERP TELEPHONE & ELECTRICAL WORKS, of
12, Rue de Verger, Antwerp, in the Kingdom of Belgium.
I, ALFRED JULIUS BOULT, of 111, Hatton Garden, in the County of Middlesex,
Chartered Patent Agent, 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 an electric indicator or annunciator intended chiefly for
large exchange stations for telephonic installations.
This indicator is characterised by the arrangement of a single electro-magnet
constituted by two coils one within the other on a common core with two poles and
of two armatures operating only by their electro-magnetic action the contact of the
armature being directly connected to one of them and ensuring a certain and
energetic action.
In the accompanying drawing Fig. 1 is a longitudinal section of the auto-electric
indicator provided with a contact according to the present invention.
Fig. 2 is a plan.
The core N on which the two coils X Z are arranged is enclosed in a metallic
casing G and insulated from it by ebonite rings M M. The casing G forms a frame
or support to which are secured all the other accessories comprising attachments I
and P, armatures 0 and S, and ebonite support J for a blade contact A and B.
The armature O is freely suspended between the points of two pivot screws U U
(Fig. 2) and its distance from the core N is adjustable by means of a set screw R
a gun metal screw R¹ passing through the centre of the armature preventing it
from adhering to the core. At its lower end the armature carries on a rigid exten-
sion rod an ebonite contact block Q resting on the contact blade A which, as well
as the other blade B is mounted in the ebonite support J so as to form a spring
and normally maintain the armature 0 out of contact with the core. The two
blades are provided with platinum contacts and one of them A is connected with
the end of the wire of the coil Z by means of a plug H, and the other one, 'B,
with the other end of this coil by means of the plug H' so that by means of these
two plugs the coil Z may be inserted into the circuit of a local battery while the
coil X which is wound in the ordinary manner as the subscriber's indicator or
that at the exchange station is inserted by means of plugs F F into the line
circuit.
The opposite end of the core N is provided with a projection u controlling the
wedge shaped armature S secured to a shutter or flap V (normally masking the
number of the subscriber on the part P) and pivoted together with the latter
at the point i. The armature is moreover provided with a small rod t by means
of which it closes when in its call position the circuit of an alarm or of a night call
indicator by coming in contact with the pin or rod T.
The working of the apparatus is as follows:-

page_text: When a subscriber sends a current into the line it passes through the coil X
which magnetises the core N causing the armature 0 to be attracted in consequence
of which the contact piece Q depresses the blade A the platinum plate of which
produces contact with the platinum point of the blade B thus closing the circuit
of the local battery which circuit passes through the coil Z and strongly magnetises
the core N making the contact A B still more complete the projection u of the core
causing the armature S to swing down and the shutter V to be raised so that the
subscriber's number is uncovered the circuit T t being closed at the same time.
A small copper knob r prevents the armature from adhering to the core.
It will be seen that the efficient working of the apparatus depends on the
complete and sustained closing of the local battery. circuit so that the contact must
be always kept clean.
To this end the two blades A and B are very long and flexible so that when the
blade A is depressed by the armature O the blade B is also depressed but to a lesser
extent so that there is produced a rubbing action and friction of the platinum point
on the platinum plate or washer so that the contact is thoroughly cleaned at each
operation of the apparatus.
The circuit Ttis that of an alarm or other call-apparatus attracting the attention
of the attendant who goes to the instrument and automatically breaks (by any
suitable device such as a key or contact breaker) the local circuit of the battery so
that the magnetism by the coil Z ceases and the shutter V falls again and thus
covers the call number; the armature 0 at the same time returning to its initial
position.
The general circuit only serves to establish the contact of the blades A B for
closing the circuit of the local battery this circuit being broken by the attendant
as soon as he answers the call. This principal circuit has therefore no action on
the annunciator as long as the local circuit is broken.
Having now particularly described and ascertained the nature of the said
invention as communication to me by my foreign correspondents and in what
manner the same is to be performed, I declare that what I claim is :-
-
1. An electric indicator for exchange stations of telephonic installations compris-
ing a single electro-magnet with two coils arranged one within the other on a
common core having two poles with electro-magnetic action both for closing the
circuit of the local battery and for raising the shutter and simultaneous closing of
an indicator circuit substantially as described.
2. In an indicator of the character described the arrangement in the circuit of
the local battery of a contact comprising two long flexible blades operated by an
ebonite block secured to one of the armatures for interrupting and closing said
circuit the platinum contact surfaces of the blades rubbing against and cleaning
each other at each operation of the apparatus owing to the unequal bending
movement of the blade substantially as described.
3. In an electric indicator of, the character described the combination of a
projecting pole. of the core with a pivoted wedge shaped armature carried by the
shutter and a contact rod simultaneously closing the indicator circuit substantially
as described.
4...The combination and arrangement of parts constituting the complete electric
indicator device substantially, as described; or illustrated in Figures 1 and 2 of the
accompanying drawings.