Improvements in Telephonic Inter-communication System.
Year: 1898

page_text: PROVISIONAL SPECIFICATION.
Improvements in Telephonic Inter-communication System.
I, WILLIAM AITKEN, of Oxford Court, Cannon Street, in the City of London,
Engineer, do hereby declare the nature of this invention to be as follows:-
-
This invention relates to improvements in telephonic inter-communication
systems, to be chiefly used as a house or similar installation, characterized by a
special construction and arrangement of telephonic apparatus whereby communica-
tion can be established without a central switch, and has for its object the
simplification and improvement of the apparatus and circuits, and the attain-
ment of better results. For inter-communication systems heretofore employed it
has been possible for any of the stations to overhear the conversation between
any two stations or telephones previously connected by manipulating the switches
or plungers at their apparatus. In a system constructed according to my invention
perfect secrecy is obtained and a distinctive signal given to the party desiring
communication should the station required be already engaged in a conversa-
tion with a third station, this signal being obtained without interrupting
the conversation.
To attain this end I provide at each terminal station as many jacks as there are
stations to the system the intermediate stations having one extra. I preferably
use what are commonly known as five point make and break jacks. All the
jacks relating to the same station are joined together by a twisted pair of wires
which are connected as follows:-
On No. 1 line, the wires are connected between the line springs of No. 1 jack
at No. 1 station, and the line springs of No. 1 jack at No. 2 station, the inner
contacts of this jack being joined to the line springs of No. 1 jack at No. 3 station,
and so on. On No. 3 line (and on all intermediate station lines) there are two
home or answering jacks, the line springs of the left hand jack being
joined to the line springs of No. 3 jack at No. 2 station, and the
line springs of the right hand jack being connected to the lines springs
of No. 3 jack at No. 4 station and so on as before. The wires end on the line
springs of the jacks farthest from the home jacks. One of the line springs is
connected to the tab of the barrel or bush of each jack. The inner contacts of the
home jacks are joined together and connected through a bell or indicator and
common battery to earth or common return. The two bells at the intermediate
stations are of different tones.
The instrument has the receiver and the secondary of the transmitter induction
coil differentially wound and joined together in the well known manner, with the
centre point of the receiver joined to one side of the ringing battery, the line ends
of the induction coil being joined to the tip and sleeve of a two-way plug, the
primary and the microphone being joined to a speaking battery in the usual
War.
Suppose No. 1 wishes to speak to No. 5. With the receiver against the ear
No. 1 places the tip of the plug against the barrel or bush of the jack. If the

page_text: receiver is silent the line is engaged, and must not be interfered with. If, however,
there is a clicking or burring sound in the receiver, the plug can be inserted as
the line is idle. The circuit in the second case is from the ringing battery,
through bell through one contact and spring of each jack of the line tested in
series, to barrel of jack, tip of plug and through one coil of receiver to centre point
and thence to other side of battery. The plug may then be inserted, and
communication established.
The battery and circuit resistance may be so adjusted that a click only is obtained
in the receiver when testing a line, the station wanted being rung up when the plug
is fully inserted the total resistance then being halved. The current is then over
the two wires, two halves of secondary of induction coil and through the two coils
of the receiver in parallel. The receiver being differentially wound the diaphragm
would not be affected by the ringing current. Ordinary receivers with centre point
may be used but the diaphragm would be vibrated by the ringing current.
My invention admits of various modifications e.g. three point make and break
jacks may be used and one line wired in parallel to all bushes, and the other
in series with the contacts and springs, the contact and the bush or barrel of the
last jacks being joined together, the home jacks having the contacts joined to
bell or indicator as before described. A bar of metal is fitted say "in front and
a little below the bushes of the jacks and joined to one side of the ringing battery.
Any ordinary pattern of instrument is used. The line wanted is tested and the bell
rung by placing the tip of the plug against the bush of the jack and at the same
time allowing the sleeve of the plug to rest on the above mentioned bar.
My invention may be used without transmitter induction coils and with a
common speaking battery.
101
1
ec
1000
I, WILLIAM AITKEN, of Oxford Court, Cannon Street, in the City of London,
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:
This invention relates to improvements in telephonic inter-communication
systems to be chiefly used as a house or similar installation, characterised by a
special construction and arrangements of telephonic apparatus whereby communica-
tion can be established without a central switch, and has for its object the
simplification and improvement of suitable apparatus and circuits, and the attain-
ment of better results. For inter-communication systems heretofore employed it
has been possible for any of the stations to overhear the conversation between
any two stations or telephones previously connected by manipulating the switches
or plungers at their apparatus. In a system constructed according to my invention
perfect secrecy is obtained and a distinctive signal given to the party desiring
communication should the station required be already engaged in a conversa-
tion with a third station, this signal being obtained without interrupting
or only interrupting momentarily the conversation.
My invention is illustrated by the accompanying drawings.
Fig. 1, being a diagrammatic representation of an installation having three
stations which for the sake of clearness shows only the complete circuit of one
instrument, using branching jacks, but with break jacks for answering.

page_text: Fig. 6, snows an alternative arrangement or relay and bridging coil for Fig. 1,
circuit.
Fig. 3, shows a modification using break jacks and having a different form of
engage test.
Fig. 4, shows a section of a jack strip with plug in the testing and ringing
position.
Fig. 5, shows a section of a jack strip with plug in the through position.
Similar parts are indicated by similar letters and figures in the various drawings.
Fig. 1, shows one arrangement of the apparatus according to my invention using
branching jacks at all stations on each circuit except at the home or answering
station where a make and break jack is used for the purpose to be hereinafter
described, one such jack being used for each circuit. One branching jack is fitted
at each station for each circuit the a spring of No. 3 jack at No. 1 station being
connected to the a spring of No. 3 jack at No. 2 station and to the a spring of
No. 3 jack at No. 3 station, and so on to the a springs of the No. 3 jacks at each
station. The 6 springs are connected together in a similar manner. The inner
contacts of the a and b springs of the No. 3 jack of No. 3 station, which is the
home or answering jack, are joined together and connected to one side of a trem-
bling bell g of the well known pattern, the other side of which in common with all the
other bells g, is joined to one side of the battery h. The spring c has a connection to
the centre point of the receiver j, and its under contact is joined through
resistance k to common return to battery h. The upper contact of spring c has a
connection to the outer contact of relay f the armature being connected through one
winding of the coils (or through one coil as in Fig. 2) to the battery side of bell g.
One winding of the coils of relay f, or one coil as shown in Fig. 2 being connected
by wires d and e as a bridge between the two wires of the circuit. This second
winding of the relay for the second coil as in Figure 2 may be omitted if the receiver
is not differentially wound. The relay may be omitted and the connection made
between the bell g and the outer contact of spring c but preferably I use the relay
because it is more easily regulated. Plug has the tip and sleeve connected to
opposite sides of the induction coil and receiver j of a telephone instrument, these
parts being preferably, though not necessarily, differentially wound.
resistance k may have a short circuiting key l for calling.
C
The
The operating is as follows:-Supposing No. 1 station desires to speak to No. 3.
No. 1 inserts service plug in No. 3 jack and with a suitable battery h bell q
responds. To allow of a smaller battery being used the plug i may be inserted and
short circuiting key depressed when bell g responds. No. 3 inserts service plug
in jack 3 and bell g is thereby cut out of circuit and relay f substituted. This
relay is of such resistance and so adjusted that it does not respond and the circuit
is complete for communication. If No. 2 now desires to talk to say No. 3 he will
momentarily touch the front of jack with tip of plug and the relay f vibrates
advising him that the line is engaged and also advising No. 1 and No. 3 that
the line is being tapped. It is therefore impossible for any station to overhear the
conversation of another. The reason for the relay f responding now is that the
resistance of the battery circuit is nearly halved as there is a path through k of
station and of station 2 over the line springs 6 through sleeve of plug i
station, 3 through half of coil and receiver j, through spring c and its upper
contact through relay f and so back to battery h. Should a subscriber omit to
withdraw a plug after a communication he may be called by inserting a plug in
a jack connected with his line and depressing short circuiting key 7 thereby causing
relay to vibrate the diaphgram of his receiver. All the jacks relating to the
same station are joined together by a twisted pair of wires.
Fig. 3 shows my invention worked by make and break jacks through, and two
jacks used as the home or answering jacks. In this modification the common
return consists of a metallic strip p fitted in front of each strip of jacks as shewn
at Figs. 4 and 5 instead of being connected to the centre points of the receivers
as in Figure 1.

page_text: All the jacks relating to the same station are joined together by a twisted pair
of wires which are connected as follows:
On No. 1 line, the wires are connected between the line springs a and b of No. 1 jack
at No. 1 station and the line springs a and b of No. 1 jack at No. 2 station the inner
contacts of this jack being joined to the line springs a and b of No. 1 jack at
No. 3 station and so on. On No. 3 line (and on all intermediate station lines)
there are two home or answering jacks, the line springs a and b of the left hand
jack being joined to the line springs a and b of the No. 3 jack at No. 2 station, and
the line springs a and b of the right hand jack being connected to the line
springs a and b of No. 3 jack at No. 4 station, and so on as before. The wires end
on the line springs a and b of the jacks farthest from the home jacks. One of the
line springs (6) is connected to the tab of the barrel or bush of each jack except in
the case of the home jacks. The inner contacts of the home jacks are joined
together and connected to the c spring of the other home jack and its under contact
to a bell or indicator g, and common battery h, to common return p.
The two
bells g and g at the intermediate stations are of different tones. Any of the well
known forms of instruments may be used, connected to a service plug i.
Suppose No. 1 wishes to speak to No. 3. With the receiver against the ear,
No. 1 places the tip of the plug against the barrel or bush of the jack and allowing
the sleeve to touch the common return p. If the receiver is silent the line is
engaged and must not be interfered with. If, however, there is a burring sound
in the receiver, owing to the bell 9 responding the plug can be inserted as the
line is idle. The circuit in the second case is from the ringing battery h, through
bell g through one contact and spring b of each jack of the line in series, to barrel
of jack, tip of plug i and through receiver and coil j to sleeve and common return p
and thence to other side of battery h. The plug may then be inserted, No. 3 station
on hearing the bell ring inserts the service plug into the corresponding jack and
communication is established. The two home jacks are necessary to make the
service a secret one, all stations on the right being cut off when speaking to a
station on the left and vice versa.
Although I preferably use springs jacks operated by a service plug connected
with the instrument, extra springs might be added to the spring jacks and
connected to the telephone and a fixed plunger or key over each set of springs.
This invention admits of other modifications in the arrangements which would
readily suggest themselves to those skilled in the art. I therefore do not limit
myself to the precise arrangements shown or described herein.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is:
(1) The improved system of telephonie inter-communication substantially as
hereinbefore described under several modifications with reference to the annexed
diagrams.
(2) The improved engaged test which admits of branching jacks being used and
yet prevents a third station overhearing a conversation between any other two
stations substantially as described and as shewn in the accompanying drawings.
Dated this 16th day of December 1898.
WILLIAM AITKEN,
Applicant.