An Improved Automatic Electrical Call Apparatus, Principally for Use in Telephone Circuits.
Year: 1892

page_text: Date of Application, 7th Dec., 1892
Complete Specification Left, 1st Sept., 1893-Accepted, 7th Dec., 1893
PROVISIONAL SPECIFICATION.
An Improved Automatic Electrical Call Apparatus, Principally for
Use in Telephone Circuits.
NAI KHEM 59 Wilson Street Derby in the County of Derbyshire Electrical
Engineer do hereby declare the nature of this invention to be as follows:-
In the ordinary arrangement of a telephone circuits the receiver by its own
weight is made to actuate a switch, which connects the call bell with the line wire ;
it necessarily follows that if the user of a telephone fails to hang the receiver on
the hook which actuates the bell switch that his call bell is left disconnected and
that any place such as the Exchange will not be able to attract his attention until
he restores the receiver to the hook.
My invention relates to a method by which the call bell of any telephone user is
by electric automatic means always available.
This is accomplished by the following device :-The current from the line is
conducted to an electro-magnet (A) after passing through which it passes to earth
(or through a relay or call bell if desired) the movement of a lever with which
the armature of this electro magnet is provided causes this connection to be
interrupted on the cessation of the current, but at the same time automatically
connects to earth a second electromagnet (B) this being in circuit with the
telephone receiver. The resistance of the electro-magnet (B) is so arranged as
not to be effected by the telephonic current. If now a bell current be sent along
the line it will pass through the coils of the electromagnet (B) which will
automatically bring the armature of the electromagnet (A) into its normal position.
In brief the electromagnet (A) brings into circuit electro magnet B & the receiver.
The "ring off" current passing through electromagnet (B) again brings the
electromaguet A into circuit and at the same time cuts itself out of circuit and also
the receiver. It must be seen that the telephone receiver is thus out of circuit
whether the telephone receiver be returned to the hook or not providing a ring off
current is sent while the call bell will never under any circumstances be out of
circuit. The automatic device by which A put B into circuit and vice versa is
accomplished by a system of levers & electrical contacts controlled by the
armatures.
In the case when it is not necessary that the receiver shall be out of circuit
except when speaking I dispense with the electro magnet A using B as a bell
relay which I join in series or parallel circuit with the telephone as in the above
case.
COMPLETE SPECIFICATION.
An Improved Automatic Electrical Call Apparatus, Principally for
Use in Telephone Circuits.
NAI KHEM of 59 Wilson Street Derby in the County of Derbyshire 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 :-
In the ordinary arrangement of a telephone circuit the receiver by its own
•

page_text: weight is made to actuate a switch which connects the call bell with the line wire.
It necessary follows that if the user of a telephone fails to hang the receiver on the
hook which actuates the bell switch his call bell is left disconnected and that any
place such as the Exchange will not be able to attract his attention until he restore
the receiver to the hook.
My invention relates to a method by which the call bell of any telephone user is
by automatical means always left available.
This is accomplished by the following device. The current from the line is
conducted to an electro magnet marked "A" on diagram after passing
through which it passes through the levers L₁ & L, to earth or through
relay or call bell if desired. The movement of the lever Li with which the
armature "A" of this electro magnet "A" is provided causes the connection at
the contact "C" between L₁ & L₂ to be interrupted on the cessation of the
current, but at the same time automatically connects to earth the electro
magnet "B" this being in circuit with the telephone receiver (either in series or
parallel). The resistance of the electro magnet "B" is so arranged as not to be
affected by the telephonic current.
"
If now a bell current be sent along the line it will pass through electro-magnet B.
which will bring the armature "a" of electro magnet "A" into its original normal
position by means of the armature "B" & lever L3 belonging to electro
magnet "B." In brief the electro magnet "A brings into circuit electro
magnet "B" & the telephone receiver. The "ring off" current passing through
"B" again bring "A" into circuit at the same time cut itself out of circuit and
also the receiver "R." It will thus be seen that the telephone is out of circuit
whether the telephone be returned to the hook or not provide that a "ring off"
current is sent. The call bell will under any circumstances never be out of
circuit.
The automatic device by which the electro-magnet "A" puts the electro-
magnet "B" into circuit & vice versa is accomplished by a simple system of
levers L₁ L, & L. & electrical contacts "C" & "D" controlled by the
armatures "A" and "B."
"
I will now describe in greater detail the precise manner in which the apparatus
is worked. An "incoming current passes through electro magnet "A to the
-lever Land through the contact point at "C" through lever L, and call bell (or
relay) to earth. The armature "A" is at the-same-time-attracted_and_allows the
Lever L₁ turning about the point "p to release the lever L, pivoted at "p"
which on falling down makes contact with screw "D." On the cessation of the
current, the lever L₁ falls away from its contact with lever L, L, being stopped
from falling down by screw "Ě."
"
When the ring off current enters the instrument at terminal "T" it can no
longer pass through "A" but passes through electro magnet B thence through L
& contact screw "D" & call bell or relay to earth, as shown. At the same time
the electro magnet "B" attracts the armature "B" & lever L, is drawn back
lifting up L₁ into contact with L, at the contact point "C" & breaking contact
at " D." In fact it goes back to its original or normal position.
The telephone receiver may be arranged either in series or parallel with electro
magnet "B."
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed I declare that what I
claim is :-
1. The method of employing two electro-magnets with combined levers so
arranged that when a current passes through either of these electro magnets it is,
on the cessation of the current thrown out of circuit and the other brought into
circuit.

page_text: 5
2. The arrangement of electro-magnets & levers for accomplishing this as shown
in the diagram and substantially as described.
3. The combination of electro magnetic arrangement substantially as described
with telephone circuits more particularly for signalling purposes.
Dated this 30th day of July 1893.
NAI KHEM.