A system is presented for automatically controlling transformer coupled alternating current electric lines. The secondary winding of each transformer is provided with a center tap. A switching circuit is connected to the center taps of a pair of secondary windings and includes a switch controller. An impedance is connected between the center taps of the opposite pair of secondary windings. The switching circuit has continuity when the AC lines are continuous and discontinuity with any disconnect of the AC lines. Normally open switching means are provided in at least one AC line. The switch controller automatically opens the switching means when the AC lines become separated

Dwinell, W. S.

English

NASA Technical Reports Server

4 
United States Patent 1191 
Dwinell 
[I11 4,161,661 
[45] Jul. 17, 1979 
[54] SYSTEM FOR AUTOMATICALLY 
SWITCHING TRANSFORMER COUPLED 
5- 
[76] Inventors: Robert A. Frosch, Administrator of 
the National Aeronautics and Space 
Administration, with respect to an 
invention of William S. Dwinell, 
Santa Ana, Calif. 
[21] Appl. No.: 885,067 
[22] Filed Mar. 9,1978 
1511 Int. c1.2 ............................................... HOlH 3/16 
- 1  
[52] U.S. c1. ...................................... 307/119; 307/98; 
361/170 
[58] Field of Search ................. 307/112, 113, 98, 125, 
307/140, 119; 340/652, 538; 361/156, 170, 194 
[561 References Cited 
U.S. PATENT DOCUMENTS 
3,160,795 12/1964 Awe .................................... 361/156 
Primaly Examiner-L. T. Hix 
Assistant Examiner-S. D. Schreyer 
Attorney, Agent, or Firm-Marvin J. Marnock; John R. 
Manning; Marvin F. Matthews 
[571 ABSTRACT 
A system is provided for automatically controlling 
transformer coupled alternating-current electric lines. 
The secondary winding of each transformer is provided 
with a center tap. A switching circuit is connected to 
the center taps of a pair of secondary windings and 
includes a switch controller. An impedance is con- 
nected between the center taps of the opposite pair of 
secondary windings. The switching circuit has continu- 
ity when the AC lines are continuous and discontinuity 
with any disconnect of the AC lines. Normally-open 
switching means are provided in at least one AC line. 
The switch controller automatically opens the switch- 
ing means when the AC lines become separated. 
6 Claims, 2 Drawing Figures 
https://ntrs.nasa.gov/search.jsp?R=19790020244 2020-03-20T19:18:15+00:00Z
U.S. Patent Jul. 17, 1979 4,161,661 
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FIG. 2. 
4,161,661 
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when the connector separates following, for example, 
the launching of the space vehicle. SYSTEM FOR AUTOMATICALLY SWITCHING 
TRANSFORMER COUPLED LIMES BRIEF DESCRIPTION OF THE DRAWINGS 
ORIGIN OF THE INVENTION 
The invention described herein was made in the per- 
formance of work under a NASA contract and is sub- 
ject t6 the provisions of Section 305 of the National 
Aeronautics and Space Act of 1958, Public Law 85-568 
(72 Stat. 435; 45 U.S.C. 2457). 
5 FIG. 1 is a schematic representation of a preferred 
system for automatically switching transformer-cou- 
pled AC lines in accordance with the invention; and 
FIG. 2 shows the portion of the system in the space 
vehicle follow@ hunch- 
DETAILED DESCRIPTION O F  A PREFERRED 
(a) Field of the Invention As previously mentioned, the invention will be illus- 
This invention relates to systems for switching trans- trated in connection with audio lines used for carrying 
former coupled AC lines and has particular application 15 out communications between a launch station L s  and a 
to space vehicles wherein an umbilical connector cou- space vehicle SV which are interconnected through an 
pies the audio lines from the launch station to the audio umbilical cord 13 having an unlbilical connector 14 
lines in the space vehicle. comprised of two plugs 15 and 16. The equipment in the 
space vehicle has a control panel CP. 
The audio lines L1-L2 and L1’-L2’ are coupled 
the audio lines Ll-L2 and Ll’-L2’ are coupled through 
transformers Tl-T2 and Tl’-T2’, respectively. The 
prime (‘) designates that the particular item is on the side 
25 of the space vehicle. Each transformer has a primary 
winding P and a secondary winding S. 
Lines Ll’-L2’ are provided with at least one but 
preferably two normally-open switching means Sl-S2, 
respectively, for the purpose of disconnecting the lines 
An indepedent switching circuit, whose energization 30 from the transformers Tll-Tr after the plugs 15 and 16 
separate at the launch of the vehicle. 
10 
BACKGROUND O F  THE INVENTION EMBODIMENT 
(b) Description of the Prior Art 
While this invention can have application to various 20 
technical fields, wherein AC lines are transformer cou- through the l d d i c a l  cord. For purposes of isolation, 
pled, it will be illustrated in connection with audio 
communication in space vehicles. Prior to launch, 
audio lines at the launch station are coupled to audio 
lines in the space vehicle through an umbilical connec- 
tor. These audio lines at the launch station are typically 
transformer coupled to the audio lines in the space vehi- 
cle for better noise isolation. 
is controlled by a manually operated switch at the con- 
trol Pane1 Of the space In accordance with the present invention, it is desired 
troller which operates switching in the audio that the switching means become operative auto- 
a switch con- 
lines of the space vehicle to connect them to the trans- matically immediately following the uncoupling of the 
formers. Following launch, the switching circuit is 35 two plugs 15, 16. In this manner no switch need be 
disconnect the audio lines from the transformers in the 
space vehicle. 
It will be appreciated that immediately following 
launch, the crew in the 
operative functions to carry out and, therefore, the need 
to manually operate a control switch at the control 
manually de-enerdzed to cause the switching meanS to manually moved on the control panel Cp for the pur- 
pose of operating switches s1 -~2 .  
This is accomplished in accordance with the present 
invention by providing each secondary winding s with 
has numerous 40 a center tap C establishing a null point for the secondary 
winding. The center taps of transformers ~ 1 ’  and ~ 2 ’  
are connected to a switching circuit, generally desig- 
panel for de-energizing the switching Circuit ConstitUtes nated as 20. For simplicity of description, the switching 
a burden for the crew which this invention intends to circuit 20 is illustrated as comprising a switch controller 
remove. The invention also simplifies the Space vehicle 45 21, such as a relay coil 22, which when energized turns 
by eliminating the need for the switch and extra wires the switches s1-s~ ON. 
leading from the manually operated switch at the space In most applications, the switches s1-s2 and the 
vehicle’s control panel to the switching circuit. switch controller 21 will be solid state devices. The 
switching circuit 20 is energized by a power supply 24 
50 which can be DC or AC. SUMMARY O F  THE INVENTION 
The automatic switching system of this invention is At the launching station LS, the center taps of trans- 
adapted for a network having transformer-coupled AC formers T1 and T2 are interconnected by a low impe- 
lines interconnected through a mating connector. Each dance circuit, generally designated as 30, which can 
AC line is connected to the connector through the comprise a conductor 32 and a manually-operated test 
transformer having a primary winding and a center- 55 switch 34 which is normally closed. Impedance 30 pro- 
tapped secondary winding. An independent switching vides an electric path, i.e., continuity for the switching 
circuit is connected to the center taps of a pair of sec- circuit 20 when plugs 15 and 16 of the umbilical connec- 
ondary windings connected to one side of the connec- tor 14 are mated, as shown in FIG. 1. Thus, the supply 
tor. An interconnect is made to the center-taps of the current I flows from one terminal 25 of the power sup- 
opposite pair of secondary windings connected to the 60 ply 24 in the direction of the arrows, into the center tap 
other side of the connector. The switching circuit has of transformer T2’ and will flow out from the center tap 
continuity through the interconnect when the connec- of transformer T2, thence through the impedance 30 
tor is mated, and it has discontinuity when the connec- into the center tap of transformer T1. The current will 
tor is unmated. The switching means are controlled by flow out from the center tap of transformer Tl’ and will 
a switch controller forming part of the switching cir- 65 return through the relay 22 to the other terminal 27 of 
cuit. The switching means automatically turn ON or the power supply 24. 
OFF depending only on the continuity or discontinuity It will be appreciated that since null points exist at the 
in the switching circuit. This continuity is interrupted transformers’ center taps C, the current I will divide 
3 
4,16 1,66 1 
equally and will flow in opposite directions in the sec- 
ondary windings so that it will not interfere with the 
audio communications carried by the audio lines Ll-L2 
and Ll'-L2'. 
Upon launch the two plugs 15 and 16 of the umbilical 5 
connector 14 become disconnected (FIG. 2), thereby 
automatically establishing a discontinuity in the switch- 
ing circuit 20 by isolating impedance 30 therefrom, 
which has the effect of de-energizing the relay coil 22 
and allowing the switching means Sl-S2 to open. In this 10 
manner, the audio lines Ll'-L2' in the space vehicle will 
become disconnected from the unused transformers 
Tl'-T2' and associated vehicle wiring which might 
otherwise interfere with the audio communications 
within the space craft. 
The operation of the switching means Sl-S2 can be 
tested with the manually operated test switch 34. Thus 
when switch 34 is opened, the switching circuit 20 will 
have a discontinuity which simulates a vehicle launch. 
It will be appreciated by those skilled in the art that in 
accordance with this invention no manually operated 
switch need be operated at the control panel CP of the 
spacecraft in order to de-energize relay coil 22. 
The present invention can be used in monitoring 
various conditions which are equivalent to the uncou- 
pling of the connector plugs 15 and 16. The change in 
the operative condition of the switching means SGS2 
can cause, for example, an alarm. The invention there- 
fore can have general utility for monitoring events. 
What is claimed is: 
1. A system for automatically operating switching 
means in transformer-coupled AC lines interconnected 
by a two-plug connector, comprising: 
four transformers, each transformer having a primary 
winding and a center-tapped secondary winding; 
a switching circuit connected to the center taps of the 
secondary windings of a first and second trans- 
former, 
the secondary windings of the first and second trans- 
formers being connected to one plug of the connec- 
tor, 
the secondary windings of the third and fourth trans- 
formers being connected to the other plug of the 
connector; 
an electric line connected to each primary winding, a 
switching means in the lines connected to the fust 
and second transformers, 
said switching circuit including a switch controller 
for operating the switching means; 
an impedance connected between the center taps of 
the secondary windings of the third and fourth 
transformers, 
said switching circuit having continuity through said 
impedance whereby said switch controller main- 
tains said switching means in one state when said 
connector plugs are mated, and 
said switching circuit having discontinuity through 
said impedance whereby said controller maintains 
said switching means in another state when said 
plugs are unmated. 
2. The system of claim 1 wherein said impedance 
3. The system of claim 2 wherein said impedance 
4. The system of claim 2 wherein said controller is a 
5. A system for automatically switching at least one 
includes a conductor. 
includes a switch for testing said switching circuit. 
relay. 
line in a network including four lines, 
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a switching means having a normal state adapted for 
coupling the first line in the primary winding of a 
first transformer having a center-tapped secondary 
winding, 
a second line coupled to the primary winding of a 
second transformer having a center-tapped seoond- 
ary winding, 
a third line coupled to the primary winding of a third 
transformer having a center-tapped secondary 
winding, 
a fourth line coupled to the primary winding of a 
fourth transformer having a center-tapped second- 
ary winding; 
a switch circuit connected to the center taps of the 
secondary windings of the first and second trans- 
formers; 
an impedance interconnecting the center taps of the 
secondary windings of the third and fourth trans- 
formers, 
a two-plug connector interconnecting the secondary 
windings of the first, second, third and fourth trans- 
formers whereby said first line is coupled through 
said first and third transformers to said third line 
and said second line is coupled through said second 
and fourth transformers to said fourth line, 
said switching circuit including a switch controller 
for operating said switching means when the con- 
troller is energized, 
said switching circuit having circuit continuity 
through said impedance and the secondary wind- 
ings of said four transformers thereby allowing the 
switch controller to operate the switching means 
when said two plugs of the connector are mated, 
and 
said switching circuit having discontinuity when the 
two plugs are unmated thereby deenergiziig said 
switching circuit and said switch controller and 
returning said switching means to its normal state. 
6. A system for automatically operating switch means 
in transformer-coupled AC lines interconnected by a 
two-plug connector, comprising: 
a first plurality of transformers, each transformer 
having a primary winding and a center-tapped 
secondary winding, the secondary windings of said 
first plurality of transformers being connected to 
one plug of the connector, 
a second plurality of transformers, each having a 
primary winding and a center-tapped secondary 
winding, 
the secondary windings of said second plurality of 
transformers beingsonnected to the other plug of 
the connector and a different one of said AC lines 
being connected to each primary winding of said 
transformers; switch means in each of said lines 
connected to the primary windings of the first 
plurality of transformers; 
impedance means connected between the center taps 
a 
of the secondary windings of said second plurality 
of transformers; 
switching circuit means connected to the center 
taps of the secondary windings of said first plural- 
ity of transformers and having continuity through 
said plug connector and said impedance means 
when said connector plugs are mated, said switch- 
ing circuit means being adapted to operate said 
switch means and maintain said switch means in 
closed condition when energized; 
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a power supply means for energizing said switching switch means and the electric lines connected to 
the primary windings of said first plurality of trans- 
formers. 
circuit means, 
said switching circuit means having a discontinuity 
when said plugs are unmated whereby said switch- 
ing circuit means is deenergized i d  opens said 5 * * * * *  
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System for automatically switching transformer coupled lines

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