Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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DATA TRANSMISSION BUS COUPLER
This invention relates to the transmission of
data, and especially multiplexed serial data
transmission.
Such systems are increasingly becoming important
for a number of applications, for example in military
avionics, where data is sent to equipment in the
aircraft via a single data transmission bus, or data
bus, that is common to a number of items of equipment,
and a branched line or stub that connects the equipment
to the data bus.
According to the present invention, there is pro-
vided a plug-in coupler for forming a splice between a
data transmission bus of a multiplexed data trans-
mission system and a plurality of stubs, whic.h compri-
ses a generally flat housing having a pair of
disconnectable connector portions that are connected to
each other within the housing by a pair of conductors
so that an in-line splice can be formed in the data
bus, and an array of contacts for forming releasable
connections to a plurality of stubs, the contacts being
transformer coupled to the pair of conductors.
Each of the stubs is coupled to the data bus
within the housing by a transformer coupling arrange-
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ment which usually comprises an isolation transformer
and a resistance of about 50 ohms on each line between
the isolation transformer and the data bus so that a
short circuit in one of the stubs, for example caused
by damage to the equipment, will not affect the
remainder of the data transmission system.
The coupler according to the invention has the
advantage that it is particularly compact compared with
known systems that use a coupler for individual stubs.
In addition the coupler is particularly versatile in
that it can easily be removed and changed to accom-
modate alteration in the equipment that is controlled
by the system, and can be removed for testing or repla-
cement. The coupler may be made, for example, in the
form of a conventional plug-in rectangular connector
having a coupler extension mounted on an end thereof.
The connector may then be mated with a corresponding
rectangular connector e.g. on opposite sides of a bulk-
head in a conventional manner. The fact that the
coupler can be made in such a small size has the addi-
tional advantage that there is a greater choice of
location of the coupler in the aircraft. For example,
one problem with conventional databus systems is that,
although the main databus can be balanced e.g. by
appropriate impedance connections at each end, the con-
nection of stub lines to the databus disturbs the
balance, and this disturbance is worsened as the stub
length is increased. By using databus couplers
according to the invention it is possible for the main
databus to extend in a relatively convoluted path so
that it passes near (e.g. less than about 6m and pre-
ferably less than 3m) to the equipment with a con-
sequent reduction in stub length. For example in
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military aircraft it is possible to pass the databus
along the aircraft wings and provide a coupler in the
region of the missiles or other equipment rather than
to provide a long stub from a coupler in the centre of
the aircraft fuselage.
In one form of coupler according to the invention
the disconnectable connector portions and the contacts
for forming connections to the stubs are arranged
together as a single array in a connecting face of the
housing so that the stubs and the data bus may be
disconnected in a single operation. This form of
coupler is appropriate for use where the data bus is
provided for example in the equipment racking system or
where a connection can be made to the data bus via the
racking system. In an alternative form of coupler the
contacts for forming connections to the stubs are
arranged together as a single array in a connecting
face of the housing and the disconnectable connector
portions for the data bus are located at separate
points on the housing spaced apart from the connecting
face of the housing. This form of coupler is
appropriate where, for example equipment or racking for
the equipment is to be installed and the data bus
extends outside the equipment or racking. The connec-
tor portions for the data bus are preferably arranged
on opposite sides of the housing substantially in line
with each other, in order to simplify the path of the
data bus.
If, as is often the case, it is desired to screen
the cables and the interior of the coupler from
electromagnetic interference, this may easily be
achieved, for example by the arrangement described in
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our copending European patent application No.
88305402.5.
The coupler will normally contain connection con-
tacts for at least 4 stubs, preferably at least 6 stubs
but normally not more than 12 stubs and especially not
more than 8 stubs.
Two connectors in accordance with the invention
will now be described by way of example for reference
to the accompanying drawings, in which:
igure 1 is an isometric view of one form of coupler
according the the invention;
igure 2 is a schematic circuit diagram of the coupler
of figure 1;
Figure 3 is an exploded view of the coupler of figure
1 showing the electrical components;
igure 4 is a perspective view of another form of
coupler according to the invention; and
igure 5 is a circuit diagram of the connector of
figure 4.
Referring initially to figures 1 to 3 of the
accompanying drawings, a coupler 1 for forming a splice
between a data bus of a multiplexed serial data
transmission system comprises a generally flat die cast
aluminium housing 2 that is formed in three parts, a
top and bottom shell half 2 and 3, and a connector part
4 which encloses an array (not shown) of male or female
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contact elements for forming a push fit electrical con-
nection.
The coupler contains an array of eight coaxial
male or female contacts 5 and 6 each comprising a pair
of contact elements arranged coaxially, the two con-
tacts 5 being connected together within the housing by
conductors 7 so that the contacts 5 can be connected to
the main data bus in order to form an in-line splice in
the data bus when the coupler is pushed into the
socket. The six contacts 6 are each connected to the
conductors 7 via isolation transformers 8 and 52 ohm
resistors 9 mounted on a printed circuit board 10.
The connector part is provided with side lugs 11
containing screw-threaded bolts 12 for firmly fixing
the connector part 4 of the coupler to a bulkhead,
racking tray or the like that contains a mating connec-
tor socket.
An alternative form of coupler is shown in figures
4 and 5. This form of coupler has a flat housing
comprising top and bottom shell halves 2 and 3 and con-
héctor part 4 which encloses an array (not shown) of
male or female contact elements for forming a push-fit
electrica~ connection.
The housing has two disconnectable connector por-
tions 13 and 14 that are connected to each other within
the housing by conductors 7 so that an in-line splice
can be formed in a data bus that extends outside the
bulkhead, equipment or equipment racking system. In
addition, the coupler has an array of eight coaxial
male or female contacts 6 that are connected to the
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conductors 7 via isolation transformers 8 and resistors
9 which are mounted on a printed circuit board (not
shown) in the same manner as in figure 3.
As with the coupler shown in figure 1, side lugs
11 containing screw-threaded bolts 12 are provided for
fixing the connector part 4 to a bulkhead or racking
tray.
