Jack module with inductive monitor

A jack module including a switching jack subassembly and monitor jack assembly includes a printed circuit board between the subassemblies. The subassemblies and circuit board are commonly housed. The printed circuit board contains monitor circuitry. The monitor circuitry is an inductive monitor with redundant windings.

CROSS-REFERENCE TO RELATED APPLICATIONS 
The present application discloses subject matter which is also disclosed 
and claimed in U.S. Pat. No. 5,348,491. 
BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention pertains to coaxial cable jacks and more particularly to a 
coaxial cable jack module with inductive monitoring. 
2. Prior Art 
In the prior art, jack modules for coaxial cable connections are well 
known. An example of such is shown in commonly assigned U.S. Pat. No. 
4,749,968 to Burroughs. 
The Burroughs patent shows a jack module 20 which includes a configuration 
(utilizing the embodiment of FIG. 8 of the patent) having two parallel 
spaced apart central conductors connected by a switch mechanism. The 
switch mechanism electrically connects the two parallel spaced apart 
central conductors when a plug is absent from ports associated with the 
central conductors. Upon insertion of a plug into either of the ports 
associated with the two central conductors, the-switch isolates the other 
central conductor to ground. 
As shown in the Burroughs patent, jacks of the type shown therein may be 
associated with single central conductor jacks for monitoring purposes. 
When a single jack is used in a monitoring configuration, the single jack 
is connected across either a resistance or inductance circuit to one of 
the central conductors which are joined by the switching mechanism. 
Insertion of a plug into the monitor jack permits monitoring of a signal 
flowing through the two parallel central conductors without disruption of 
the signal. 
In the prior art, jack modules having a monitor central conductor joined in 
a common housing with two central conductors joined by a switch are known. 
An example of such is shown in U.S. Pat. No. 5,246,378, issued Sep. 21, 
1993. 
In the aforementioned U.S. Pat. No. 5,246,378, monitoring is provided 
across a resistive circuit. Namely, a monitor conductor is connected to a 
main signal conductor across an electrical resistor (commonly 100 ohms). A 
plug may be inserted into the housing to make electrical connection with 
the monitor conductor. Due to the resistive drop, a signal across the main 
conductor can be monitored without interruption of the signal. 
In the aforementioned U.S. Pat. No. 5,348,491, reference is made to a 
monitor network which provides for inductive monitoring. Inductive 
monitoring is preferred in certain applications since it can result in a 
lower power loss through the network. 
Unfortunately, an inductive monitoring circuit presents certain risks with 
respect to a jack module for use in telecommunications. Unlike a resistive 
monitoring circuit, an inductive monitoring circuit places an inductor in 
series with the main signal conductor. Accordingly, if an electrical 
connection between the inductor and the main signal conductor is broken, 
the signal across the main signal conductor is lost. In high bit rate 
transmissions, such a loss is undesirable since a substantial amount of a 
customer's communications or data would be lost. This risk is normally not 
associated with resistive monitors since the monitor circuit is connected 
in parallel across a resistance. As a result, if the connection of the 
resistor to the main signal conductor is broken, the main signal conductor 
itself is not broken and there is no signal loss. 
In monitoring circuits using inductive monitoring, windings are provided 
around magnetic cores. The windings are very fragile conductors which 
typically may be connected to a printed circuit board by stamping the ends 
of the winding to flatten the ends prior to soldering onto a contact pad 
on a printed circuit board. This presents a higher risk of breakage since 
a small wire is used which is susceptible to thermal stresses, vibration 
and mechanical shock. 
It is an object of the present invention to provide an inductive monitoring 
circuit which is less susceptible to signal interruption. 
SUMMARY OF THE INVENTION 
According to a preferred embodiment of the present invention, a digital 
signal jack is provided having a housing with a signal port formed in the 
housing and sized to receive a jack plug. A first signal conductor is 
contained within the housing and aligned with the signal port for the 
first signal conductor to electrically engage a jack plug upon insertion 
of the plug within the signal port. A second signal conductor is contained 
within the housing and terminates at a connector for connecting the second 
signal conductor to a coax cable. A monitor port is formed in the housing 
and sized to receive a jack plug. A monitor conductor is contained within 
the housing and aligned with the monitor port to electrically engage a 
jack plug. A monitor circuit includes first and second electrically 
conductive windings each having first and second ends electrically 
connected to the first and second signal conductors, respectively. At 
least a third electrically conductive winding is connected to the monitor 
conductor. The first and second windings are inductively coupled with the 
third winding.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
A. General 
Referring now to the several drawing figures in which identical elements 
are numbered identically throughout, a description of the preferred 
embodiment of the present invention will now be provided. Prior to the 
discussion of the monitoring circuit of the present invention, the jack 
module in which the monitoring circuit is used will first be described 
with the description being substantially the same as that appearing in 
U.S. Pat. No. 5,348,491. 
B. Description of Jack Module 
With initial reference to FIGS. 1 through 4 and 4A, the jack module 10 is 
shown. The jack module 10 includes a first jack subassembly 12 and a 
second jack subassembly 14 commonly joined in the jack module 10 by means 
of a first shell half 16 and a second shell half 18. The shell halves 
16,18 also house a printed circuit board 20 as will be more fully 
described. The shell halves 16,18 are joined together by nut and bolt 
fasteners 22. 
As will become more fully apparent, the jack module 10 has the circuitry 24 
shown in FIG. 4A. Schematically shown in FIG. 4A, the circuitry 24 
includes a first (or IN) central conductor 26, a second (or more commonly 
referred to as OUT) central conductor 28 and a third (or more commonly 
referred to as a monitor or MON) central conductor 30. 
The circuitry 24 further includes a switch mechanism 32 including a normal 
spring 34 electrically connecting conductors 26,28. A ground spring 36 is 
positioned to urge spring 34 away from conductor 28 upon connection of a 
jack plug to conductor 28. Similarly, ground spring 36 is disposed to urge 
normal spring 34 away from central conductor 26 upon connection of a jack 
plug to central conductor 26. 
The ground spring 36 is connected to an electrical ground across a resistor 
38. Commonly, resistor 38 is 75 ohms to be compatible with North American 
telecommunication network standards. 
The circuitry further includes a monitor network 40 electrically connected 
to both the out central conductor 28 and the monitor central conductor 30. 
The monitor network 40 permits a jack plug to be connected to monitor 
central conductor 30 to monitor the signal flowing in central conductor 28 
without interruption of the signal flowing in central conductor 28. For 
use in a high bit rate application, an inductance monitor network 40 is 
preferred since it results in a lower power loss through the network 40. 
First jack subassembly 12 and the switch mechanism 32 are very similar to 
the structure shown in commonly assigned U.S. Pat. No. 4,749,968 to 
Burroughs the teachings of which are incorporated herein by reference. The 
first jack subassembly 12 is best described with reference to FIGS. 5 
through 8. 
Unless otherwise indicated, all elements of subassembly 12 (as well as all 
other elements of module 10) are metallic and electrically conductive. 
FIGS. 5 and 6 show the front half 42 of the first jack subassembly 12. The 
front half 42 includes a front casting 44 having two generally 
semicylindrical shells 46,48 which are a parallel aligned to one another 
and each associated with a cylindrical jack port 50,52. First and second 
front center conductors 54,56 are mounted within the front casting 44 and 
supported by dielectric insulators 58,60. 
Shown best in FIG. 6, first front center conductor 54 is supported in 
insulator 58 to be coaxially aligned with the axes of cylinder 52 and 
semicylinder 48. Similarly, second front center conductor 56 is supported 
by insulator 60 to be coaxially aligned with cylinder 50 and semicylinder 
46. In the assembled front half 42 as shown in FIG. 6, the semicylindrical 
portions 46,48 are aligned for their interior surface to oppose one 
another and provide a unobstructed space 62 between the front center 
conductors 54,56. The space 62 is sized to receive the switch mechanism 
32. 
Not shown in the assembly of FIGS. 5 and 6, but shown separately in FIGS. 9 
and 10, and assembled in the view of FIG. 4, is a ground clip 64 which 
includes two generally semi-cylindrical portions 66,68 joined by a flat 
body portion 70. The ground clip 64 is sized for the portions 66,68 to 
surround the semicylindrical portions 46,48 of front casting 44 with the 
ground clip 64 received within a recess 72 formed in the front casting 44. 
The front casting 44 includes cutouts 74,76. Protrusions 78,80 are formed 
on semicylindrical portions 66,68 of ground clip 64. The protrusions 78,80 
are positioned to be received within cutouts 74,76, respectively, as shown 
in FIG. 4. 
With the front half 42 of the subassembly 12 being thus described, a jack 
plug of standard industry dimensions may be received within either of 
ports 50,52. Insertion of a jack plug (not shown) into port 50 results in 
the center pin of the jack plug being received within the front half 
center conductor 56 and electrically connected thereto. Further, the outer 
casing the jack plug urges against protrusion 78 to securely receive the 
jack plug within the port 50 as well as ground the outer casing of the 
jack plug. Similar connection to a jack plug is provided by insertion of a 
jack plug into port 52 with the center pin of the jack plug electrically 
connected to front half center conductor 54 and with the casing of the 
jack plug grounded to protrusion 80 of the ground clip 64. 
The first jack subassembly 12 further includes a rear half 86 shown in 
FIGS. 7 and 8. The rear half 86 includes a rear casting 88, and first and 
second rear center conductors 94,96 having first and second retaining 
rings 98,100. Finally, the rear half 86 includes first and second 
insulating spacers 102,104 and first and second connectors 90,92. 
Shown best in FIGS. 7, 8, 11 and 12, the rear casting 88 includes a front 
retaining flange 106 and an intermediate retaining flange 108 joined by 
semicylindrical supports 110,112. Extending from the rear of intermediate 
support flange 108 are first and second open cups 114,116 each sized to 
receive a flange 91,93 of rear connectors 90,92, respectively. 
In FIG. 8, flanges 91,93 are shown received within cups 114,116. The 
connectors 90,92 (which are well-known BNC connectors) may be secured to 
the rear casting 88 by means of "coining" the cups 114,116 over the 
flanges 91,93. The phrase "coining" will be recognized by those skilled in 
the art as pertaining to rolling the edges of the cups 114,116 over the 
flanges 91,93 to mechanically secure the rear connectors 90,92 to the rear 
casting 88. Bores 118,120 are formed through the rear casting 88 with the 
bores 118,120 disposed to be coaxially aligned with the rear connectors 
90,92. The rear center conductors 94,96 are retained within the bores 
118,120 and spaced from the walls of the rear casting 88 by means of 
dielectric insulating spacers 102,104. The rear center conductors 94,96 
pass through the spacers 102,104 with the spacers 102,104 retained within 
the rear connectors 90,92 forming the completed rear portion 86 of FIG. 8. 
The rings 98,100 of FIG. 7 snap onto the pin-receiving ends 95,97 of the 
rear central conductors 94,96 to prevent extensive flaring of the ends 
95,97 as center pins (not shown) of coaxial cables (not shown) are 
inserted into the ends 95,97. 
The complete first subassembly 12 is shown in FIG. 4 with front half 42 and 
rear half 86 joined in proper alignment. A wire 55 connects front and rear 
conductors 54,96 for the conductors 54,56 and wire 55 to define the IN 
conductor 26 of FIG. 4A. Wires 57,59 connect the front and rear conductors 
56,94, respectively, to the printed circuit board 20 with the conductors 
56,94 and wires 57,59 and circuitry of the printed circuit board 20 
defining the OUT conductor 28 of FIG. 4A which remains a closed circuit 
even if a plug is connected to the MON conductor 30. 
The switch mechanism 32 is received within space 62 with normal spring 34 
biased against both forward center conductors 54,56. The normal spring 34 
and ground spring 36 are retained in a dielectric insulating housing 33 
secured in place by a nut and bolt fastener 22. The shell halves 16,18 
have grooves 428 and ribs 430 (see FIGS. 17,20) positioned to reside in 
area 62 when the first jack subassembly 12 is assembled between the halves 
16,18. The grooves 428 and ribs 430 mate with the dielectric housing 33. 
Dielectric cams 37 are provided on ground spring 36. Insertion of a plug 
into port 50 causes the plug to act against the cam 37 to thereby push 
ground spring 36 to push against normal spring 34 and urge the normal 
spring away from front center conductor 56 and causing conductor 54 to be 
connected across a resistance to ground. Insertion of a plug into port 52 
results in a similar operation with conductor 56 becoming grounded. 
The second jack subassembly 14 includes a jack unit 130 in combination with 
a barrel 132. The jack unit 130 is shown in FIGS. 13, 14 and the barrel 
unit is shown separately in FIG. 16. 
The jack unit 130 includes a grounding portion 134 having a cup end 136 and 
a plurality of finger springs 138 disposed in a generally cylindrical 
array and connected to the cup portion 136 by a semicylindrical extension 
140. The cup portion 136 has a bore 142 extending axially therethrough and 
coaxially aligned with the axis of the cylinder defined by the finger 
springs 138. 
A forward center conductor 144 secured to a dielectric insulating spacer 
146 is disposed within the cylinder defined by the finger springs 138. The 
center conductor 144 maintained generally coaxially aligned with the 
cylinder defined by the finger springs 138. 
A rear center conductor 148 extends coaxially through bore 142 and is 
spaced from the walls of bore 142 by means of a dielectric insulating 
spacer 150 through which rear center conductor 148 passes. Spacer 150 is 
retained within a BNC connector 152. The connector 152 has a flange 153 
that is received within the cup 136 and is retained on the cup 136 by 
coining the edges of the cup 136 over flange 153. Best shown in FIG. 15, a 
retaining ring 154 is received over a pin receiving end of rear conductor 
148 with the retaining ring 154 crimped into a groove 151 formed in end 
149. This manner of attaching the retaining ring 154 is identical to the 
manner of attaching the retaining rings 98,100 to ends 95,97 of the rear 
center conductors 94,96 shown in FIG. 7. 
The barrel 132 shown in FIG. 16 includes a port end 160 and a cover 162 
both of which are cylindrical and hollow and coaxially aligned separated 
by mounting tab 164. Cover 162 is sized to be received over finger springs 
138 with the finger springs 138 urged against the interior walls of cover 
162 to provide electrical grounding of grounding portion 134 to cover 162. 
A plug (not shown) inserted within port 160 has its external surfaces 
acting against the internal surfaces of finger springs 138 to electrically 
ground the casing of the plug to the fingers 138. The center pin of the 
plug (not shown) is received within conductor 144 and electrically 
connected thereto. 
Shell half 18 is shown in detail in FIGS. 17-21. Similarly, shell half 16 
is shown in detail in FIGS. 22-25. Each of the shell halves is similar. 
Each of halves 16,18 have holes 23 to receive nut and bolt fasteners 22 
when the halves 16,18 are joined. 
Shell half 18 includes a front wall 180 having three semicircular cutouts 
181. Similarly, half 16 has a front wall 182 with three semicircular 
cutouts 183. The cutouts 181,183 are positioned and sized to surround 
ports 160, 50,52 on sides thereof opposite the mounting tabs 164 and 163. 
On interior surfaces of each halves 18,16, a first groove 190 is provided 
and sized to a receive flange 47 (FIG. 5) of front casting 44 to retain 
the front casting 44 in proper alignment between the halves 18,16. A 
second groove 192 is provided in each of halves 16,18 and sized and 
positioned to receive flange 106 (FIG. 11) of rear casting 88. Finally, a 
third groove 194 is provided within each of halves 16,18 and sized and 
positioned to receive flange 108 (FIG. 11) of rear casting 88. 
Accordingly, with the flanges 47,106,108 received within grooves 190,192 
and 194 and with halves 16,18 joined together, the first jack assembly is 
securely received between the shell halves 16,18. 
Each of the halves 16,18 include rear walls 200,202 having cutouts 201,203 
to be received within a recess 205 (FIG. 11) of the rear casting 88. 
Further cutouts 201',203' are provided to receive cup end 136 (FIG. 13). 
Each of the cutouts 201',203' are provided with flats 201a',203a' 
corresponding the flats 136a on cup end 136. With the flats 201a',203a' 
opposing flats 136a, cup end 136 cannot rotate when the halves 16,18 are 
joined together. 
The barrel 132 (FIG. 16) is provided with the plurality of holes 162a 
extending therethrough at 90.degree. intervals along the outer 
circumference of the barrel 132. Interior surfaces of halves 16,18 are 
provided with raised protrusions 162b sized to be received within holes 
162a. Accordingly, the barrel 132 is fixed in a relative rotational 
position when the halves 16,18 are joined. However, during assembly, the 
position can be selected from any one of a plurality of relative angular 
positions to change the angular orientation of tab 164. 
The back walls 200,202 of halves 16,18 are provided with the cutouts 300 
between recesses 201,203. As a result, after full assembly of the halves 
16,18 around the first jack subassembly 12, gaps 302 (FIG. 2) are provided 
between opposing surfaces of the subassembly 12 and the halves 16,18. 
Through these gaps 302, conductors (such as coaxial cables, twisted pair 
cables or fiber optic conductors) can be passed to internal components as 
will become more fully apparent. 
The halves 16,18 are provided with spaces 304 disposed between the areas 
for receiving the first and second subassemblies 12,14. When the halves 
16,18 are joined, the spaces 304,305 define a cavity in which a plurality 
of electronic equipment can be received. 
In a preferred embodiment for monitoring of signals, a printed circuit 
board 20 is provided within the spaces 304,305. The shell half 18 has 
raised platforms 420,422 on opposite sides of space 304. Alignment pins 
424 project from platforms 420,422. The printed circuit board is received 
on the pins 424 and is secured to the platform by means of screws 425 
(FIG. 4) received within holes 426 formed in the platform. 
As shown in FIG. 4, in a preferred embodiment, conductor 54 is joined to 
conductor 96 by means of a wire 55 such that the wire 55, conductor 54 and 
conductor 96 form the completed first conductor 26 of the schematic of 
FIG. 4A. Forward conductor 56 of the OUT conductor 28 is connected to the 
printed circuit board 20 by means of a wire 57. Similarly, the rear 
portion of the conductor 28 is connected to the printed circuit board 20 
by means of a wire 59. In a similar manner, the forward conductor 144 of 
the monitor conductor 30 is connected to the printed circuit board 20 by 
means of the wire 400 as is the rear conductor 148 of the monitor 30 
connected to the printed circuit board 20 by means of a wire 402. With 
this arrangement, a plurality of circuitries can be provided on the 
printed circuit board 20 to ensure a variety of different monitoring 
techniques. For example, the monitor can have resistance monitoring or 
inductive monitoring (both of which are well known to those skilled in the 
art) to monitor signals along conductor 28. Also, as will be appreciated 
from reference to FIG. 4, monitoring can be achieved by inserting a plug 
into port 160 or, alternatively, connecting a coaxial cable to connector 
152. 
While the invention has been shown in a preferred manner using a printed 
circuit board having an inductive monitoring network, it will be 
appreciated by those skilled in the art that a wide variety of functions 
can be added within area 304. For example, copper to optical fiber 
conversion can be placed within this area or a balun can be placed within 
this area to permit connection to twisted pair wires. The internal 
elements within this cavity can be connected to equipment external of the 
module 10 by means of passing twisted pair cables, coaxial cables or 
optical fibers through the openings 302 formed in the rear walls of shell 
halves 16,18. 
C. Inductive Monitoring Circuit 
As previously mentioned, the aforementioned jack can be used with both an 
inductive or a resistive monitoring circuit. The object of the present 
invention is to provide an enhanced and improved inductive monitoring 
circuit for use with such jack. FIG. 27 illustrates a resistive monitoring 
circuit which includes a resistor 40' connected to a main signal conductor 
such as conductor 28 of the aforementioned jack 10. The resistor 40' 
connects the main signal conductor 28 with the monitor conductor 30. It 
would be noted that if the point of attachment of the resistor 40' to 
either of the monitor conductor 30 or the signal conductor 28 is broken, 
there is no break in the signal conductor 28. Therefore, a signal along 
the conductor 28 is not broken. In an inductive monitoring circuit, an 
inductor is placed in line with conductor 28. However, if the inductor 
winding were to break, entire signal loss along the conductor 28 would be 
lost. 
The present invention uses dual parallel and redundant inductive windings 
in the conductor 28. The present invention is illustrated schematically in 
FIG. 28 where the main signal conductor 28 is shown including halves 57,59 
and inductor 30 is shown as having halves 30a,30b. Halves 30a and 30b may 
be aligned with independent ports such as port 160 and connector 152 of 
FIG. 4. Half 57 of conductor 28 may be aligned with port 50 of FIG. 4 
while half 59 may be aligned with connector 90 of FIG. 4. 
A first conductive winding 600 and a second conductive winding 602 are each 
provided with first ends 600a,602a and second ends 600b,602b, 
respectively. The windings 600,602 are coiled such that winding 600 is in 
parallel alignment with winding 602. Ends 600a,602a are connected to half 
57. Ends 600b,602b are connected to half 59. A third winding 604 is 
provided with first end 604a and second end 604b. First end 604a is 
connected to half 30a and end 604b is connected to half 30b. The windings 
600,602 and 604 are connected to a magnetic core 608 such that windings 
600,602 are inductively coupled with winding 604. 
With the redundant windings 600,602, if either of winding 600,602 is 
broken, the remaining one of windings 600,602 retains electrical 
connection between halves 57,59 such that signal transmission along the 
main signal conductor 28 is not lost. 
FIG. 29 illustrates the preferred embodiment. In FIG. 29, printed circuit 
board 20 is shown having mounted thereon a permanent magnetic core 608. 
Circuit board 20 is the same as circuit board 20 as shown in FIG. 4. 
The first and second windings 600,602 are shown wound in parallel alignment 
with their first end 600a,602a electrically connected to a first contact 
pad 701. Similarly, second ends 600b,602b are shown electrically connected 
to a second contact pad 702. The first and second ends 604a,604b of the 
winding 604 are electrically connected to third and fourth pads 703,704. 
Circuit paths 801-804 (shown by phantom lines in FIG. 29) connect pads 
701-704 with conductors 57, 59, 30a, 30b. As a result, the circuitry of 
the schematic of FIG. 28 is achieved. 
In placing the ends of the windings 600, 602, 604 on the contact pads 
701-704, the windings'ends are first stamped such that the ends are 
flattened. Such windings are conductors with very small dimensions (e.g., 
about 0.005" diameter) such that the ends may be stamped substantially 
flat to permit welding or soldering of the ends to the contact pads on the 
printed circuit board 20. Recognizing that the mechanical flattening of 
such small wires can result in breakage of the wires due to stress or the 
like, the use of multiple windings for redundancy avoids unreasonable risk 
of breakage of both of the windings. If one winding is to break, the 
circuit path through the main circuit (i.e., along conductors 57,59) is 
not lost. 
From the foregoing detailed description of the present invention has been 
shown how the objects of the invention have been attained in a preferred 
manner. However, modifications and its equivalents of the disclosed 
concepts, such as those which readily occur to one skilled in the art are 
intended to be included within the scope of the claims.