Patent Publication Number: US-6663423-B2

Title: Stacked electrical connector for use with a filter insert

Description:
This application is a Continuation of pending application Ser. No. 09/644,485, filed Aug. 23, 2000. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to stacked electrical connectors and more particularly, to stacked electrical connectors in which a noise filter may be incorporated. 
     BACKGROUND OF THE INVENTION 
     In electronic devices containing stacked connectors, various types of filters are used to reduce or eliminate noise. Such filters may include a three terminal capacitor or a common mode choke coil. A disadvantage in the use of such filters is that they may complicate the production of the circuit board. A need, therefore, has been perceived for providing a simple means of filtering noise in stacked connectors. 
     The use of an integral ferrite element for this purpose is proposed in Japanese Patent Publication 64-2273. This reference discloses a modular jack having a modular insert installed in a casing. The body of the insert is formed with ferrite, and on one side of the insert body insert holes are formed for introducing connecting lines to be connected to respective contact springs. While this reference would appear to simplify the apparatus used for noise filtering in modular jacks, a need for further increasing the compactness of such modular jacks with integral filtering elements existed. 
     U.S. Pat. No. 5,456,619 discloses a filtered modular jack assembly having an outer insulative housing with open front and rear sides. A ferrite filtering element is positioned adjacent the rear end, and an elongated insulative insert is superimposed over the ferrite element. The insulative insert is fixed to the housing. 
     U.S. Pat. No. 6,319,064 is directed to a modular jack assembly which includes an outer insulative housing. This assembly also includes an insulative insert and an electronic filtering component mounted in a recess in the rear section of the insulative insert, which is adapted to be easily and compactly mounted in the jack. 
     Connector receptacles which are adapted to be mounted on a PWB are well known in the art. The universal serial bus (USB) connector, for example, is used in many computer and computer peripheral applications to provide for easy connection of the peripherals to computer devices. The USB connection is expected to become increasingly popular as it provides for numerous connections to the computer device without exhausting limited computer device resources. In addition, the USB connector is an excellent solution for attaching peripheral devices to portable computing devices such as notebooks. Accordingly, many computers now include two or more USB receptacles. 
     In the conventional USB connector there is essentially an insulative member which houses a plurality of contacts which extend horizontally then vertically to engage the PWB. A conductive shield has an upper wall which is superimposed over the horizontal section of the insulated insert. The conductive shield also has a lower wall adjacent the PWB, and the upper and lower walls are connected with the vertical side walls to form a plug receiving cavity. 
     U.S. Provisional Application Serial No. 60/147,830 (Attorney&#39;s Docket No. BERG-2529/C2409 US) is directed to an electrical connector system having a housing including a plurality of receiving spaces each adapted to receive a complementary electrical connector. The electrical connector system includes a plurality of contacts arranged in groups corresponding to a respective one of the receiving spaces and a common filter element connected to contacts in each of the groups. The connector also includes an outer shield that generally surrounds the housing and grounding contacts to create an electrical connection between the conductive outer shield and the plug element when inserted therein. In accordance with a feature of this application, the electrical connector system may be configured as a double deck receptacle. 
     U.S. Pat. Nos. 5,037,330, 5,167,531, 5,637,015 and 5,797,770 are illustrative of prior patents relating to stacked or double decked connectors. 
     The patents and patent applications set forth above are specifically intended to be incorporated by reference herein. 
     Commercially available modular connector systems with integrated magnetic filtering components are sold under the NETJACK® trademark by FCI Framatone Group. These connectors include magnetic components and enhanced electrical shielding which are important for EMI suppression. The magnetic components can include common mode chokes, isolation transformers, and other known filtering circuit elements. 
     While modular connector systems with integrated filter circuits are known there is a need for stacked connectors wherein the connectors are one on top of the other and have an expanded filter circuit insert capable of housing an appropriate number of filtering circuit elements. Due to the stacked nature of such connectors it is difficult to use a large insert which can include enough filtering circuit elements therein. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a stacked connector comprising a first receptacle in a first portion of the connector and a second receptacle stacked on the first receptacle in the first portion of the connector. A group of first contacts is arranged in the first receptacle and a group of second contacts is arranged in the second receptacle. A second portion of the connector is arranged adjacent to the first and second receptacles and includes a recess extending behind the first and second receptacles for receiving an insert containing at least one filtering circuit element. The groups of first and second contacts have extensions which extend into the second portion of the connector. The extensions of the first and second contacts are arranged along one wall of the recess for connection to the insert. A group of third contacts is arranged separately from the groups of first and second contacts along a different wall of the recess for connection to the insert and for connecting the stacked connector to circuitry external of the stacked connector and the insert. 
     In a preferred embodiment the first portion of the connector comprises a front portion of the connector and the second portion of the connector comprises a rear portion of the connector behind the front portion. The connector includes a top portion and a bottom portion, with the first receptacle being located in the bottom portion and the second receptacle being located in the top portion. The extensions of the first and second contacts are arranged in the top portion of the connector and the third contacts are arranged in the bottom portion of the connector. Most preferably the extensions of the first and second contacts are arranged in a row along the wall with the extensions of the first contacts alternating in the row with the extensions of the second contacts. 
     In a preferred embodiment the second contacts are arranged in the second receptacle above the first contacts in the first receptacle and corresponding first and second contacts of the receptacles are aligned in a given plane. Preferably the first and second contacts have a given width in the receptacles and a narrower width in the extensions of the contacts. The extensions of the first contacts are arranged toward one side of the first or second contacts and the extensions of the second contacts are arranged toward an opposing side of the first or second contacts. This permits the extensions of the first and second contacts to extend substantially parallel to one another to the wall of the recess without interference. 
     In a further preferred embodiment a first portion of the group of third contacts is arrange in a single row in the recess along the different wall, and a second portion of the third group of contacts is arranged in at least two substantially parallel rows for connection externally of the connector, the first portion of the third group of contacts being adapted for connection to the insert and the second portion of the third group of contacts being adapted for connection to external circuitry The contacts for external connection are arranged in a first row corresponding to the contacts in the first receptacle and a second row corresponding to the contacts in the second receptacle. Each of the contacts for external connection in the first row is preferably arranged in a common plane with a corresponding contact for external connection in the second row. The third contacts for external connection in one of the first or second rows of contacts for external connection may include a bend portion intermediate the first and second portions of the third contacts, which permits the contacts in the one of the rows to transition from a single row of third contacts at the first portion thereof to the substantially parallel rows of the third contacts at the second portion thereof. Preferably corresponding contacts in one row of the third contacts are arranged in a common plane with the corresponding contacts in the other row of third contacts. 
     In the most preferred embodiment a filter insert is provided in the recess, which is electrically connected between the extensions of the first and second contacts in the recess and the first portions of the third contacts in the recess, which are to be utilized in circuitry connected by the connector. 
     It is the aim of this invention to have an improved stacked connector for use with a filtering circuit insert. 
     It is a further aim of this invention to provide such a connector with an enlarged recess which permits a large filtering circuit insert to be utilized. 
     These and other aims will become apparent from the following description and drawings. 
     The foregoing summary, as well as the following detailed description of the preferred embodiments, is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there is shown in the drawings an embodiment that is presently preferred, in which like references numerals represent similar parts throughout the several views of the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The stacked connector assembly of the present invention is further described with reference to the accompanying drawings in which: 
     FIG. 1 is a front schematic view of a stacked connector representing a preferred embodiment of the present invention; 
     FIG. 2 is a perspective view of the stacked connector shown in FIG. 1 viewed from the rear, with the rear shield or cover bent upward; 
     FIG. 3 is an exploded perspective view of the stacked connector of FIG. 1 viewed from the rear, with the shield or cover removed; 
     FIG. 4 is a rear view of the filter insert of FIG.  3 . 
     FIG. 5 is a partial cross sectional view through  5 — 5  in FIG. 2; 
     FIG. 6 is a partial cross sectional view through  6 — 6  in FIG. 2; 
     FIG. 7 is a perspective view of a contact and its extension for use in the bottom receptacle of the stacked connector of FIG. 1; 
     FIG. 8 is a perspective view of a contact and its extension for use in the top receptacle of the stacked connector of FIG. 1; 
     FIG. 9 is a partial perspective view of the rows of contacts for connection to circuitry external of the connector of FIG. 1 viewed from the bottom of the connector; 
     FIG. 10 is a perspective view of a contact for use in the forward row of contacts shown in FIG. 9; 
     FIG. 11 is a perspective view of a contact for use in the rearward row of contacts shown in FIG. 9; 
     FIG. 12 is circuit diagram for an exemplary embodiment of a filtering insert for use in the stacked connector of this invention; 
     FIG. 13 is circuit diagram for a further exemplary embodiment of a filtering insert for use in the stacked connector of this invention; 
     FIG. 14 is circuit diagram for a still further exemplary embodiment of a filtering insert for use in the stacked connector of this invention; 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     While the present invention will hereinafter be described in connection with a preferred embodiment thereof, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims. 
     Referring to FIGS. 1 and 2 the present invention is directed to an electrical connector system  10  having a housing  12  including a plurality of receiving spaces or receptacles  14  and  16  each adapted to receive a complementary electrical connector (not shown). The electrical connector system  10  includes a plurality of contacts  18  arranged in first and second groups  20  and  22  corresponding to a respective one of the receptacles  14  or  16  and a common filter element or insert  24  connected to contacts  18  in each of the groups  20  and  22 . The connector  10  also includes an outer shield  26  that generally surrounds the housing  12  and has grounding contacts  28  to create an electrical connection between the conductive outer shield  26  and the plug element (not shown) when inserted therein. 
     While the drawings display a double deck USB connector system  10 , the present invention could be used with any type of electrical connector. While each receptacle is shown with four contacts  18  in a group  20  or  22  the invention can be employed with any desired number of contacts  18  in a group. Similarly, while two receptacles  14  and  16  are shown, the invention can be employed with any desired number of stacked receptacles. 
     Double deck receptacle  10  includes a conductive shield  26 . Preferably stamped from a single sheet of suitable conductive material, shield  26  includes a front wall  30 , a top wall  32 , bottom wall  34 , opposed lateral walls  36  and  38 , and a rear wall  40 . The front wall  30  defines a plurality of receiving spaces  14  and  16  each of which can receive a plug (not shown). The opposed lateral walls  36  and  38  each have longitudinal springs  28  bent so as to extend into the receptacle  14  or  16  opening to bear against a corresponding shield (not shown) on the plug (not shown). The bottom wall  34  also includes longitudinal springs  28  that bear against the plug shield for the same purpose. The conductive shield  26  is equipped with tabs  42  that are used to secure the shield  26  on the housing  12 . Tabs  42  also act as stand-offs to position the connector  10  relative to a PWB (not shown). Hold downs  44  aid in mounting and positioning the connector  10  with respect to the PWB. Please note that in FIGS. 5 and 6 the rear hold downs are omitted for clarity. 
     As illustrated in FIGS. 1 and 5, grounding contacts  28 ′ extend into the receiving spaces  14  and  16  from the front wall  30  of the shield  26  to provide a further electrical connection between the conductive shield  26  of the connector  10  and the shielding of a plug when inserted therein. The grounding contacts  28  and  28 ′ are formed from the conductive shield  26  and are provided to reduce electromagnetic interference. 
     As shown in FIGS. 1 through 6, the insulative housing  12  has a rear section  46  with flanges  48  and  50  that extend forwardly therefrom. The upper  50  and lower  48  flanges include front edges  52  and  54 . The upper and lower flanges  50  and  48  carry contacts  18 . Contacts  18  may be signal contacts, a power signal, or a ground contact in various combinations as desired in accordance with a particular application. Also as illustrated, a middle flange  56  extends from the insulative member  12  to separate receptacle openings  14 ,  16 . 
     Referring particularly to FIGS. 5 to  8 , the contacts  18  each include a first section  58  extending in a direction generally parallel to the flanges  48  or  50  and have a forward terminal end  60  that is engaged by the front contact retaining lip  62  of the respective flange  48  or  50 . This first section  58  also includes a convex bend  64  which extends beneath the lip  62 . The contacts  18  also include an extended section  66  or  68  which extends into a portion of the housing  12  defining a recess  70  for receiving a filter circuit insert module  72 . The contacts  18  may be supported in the housing  12  by any desired conventional means. For example, the housing  12  can be molded about the contacts  18  at a point along the first section  58  or the extended section  66  or  68  or they may be held in slots in the housing as described in the patents and applications set forth in the Background, which have incorporated by reference herein. 
     Referring again to FIGS. 1-6, the housing  12  is preferably constructed of a thermoplastic polymer having suitable insulative properties and the exterior shielding is preferably metallic. Within the walls  30  to  40  is a first portion  78  or forward open end having the receptacles  14  and  16  and a second portion  80  or rear open end defining a recess  70  for receiving the filtering circuit element or module  72 . Projecting upwardly from the bottom wall  34  in this interior section there is a medial wall generally shown at numeral  82  which separates the first portion  78  of the connector  10  from the second portion  80 . The medial wall  82  has a rear side  84  and a front side shown generally at numeral  86 . The contacts  18  are supported as described above within the medial wall  82 . The top wall  88 , bottom wall  90  and opposing lateral walls  92  and  94  of recess  70  extend rearwardly from the rear side  84  of the medial wall to form a generally rectilinear opening for receiving the insert  24 . The opening defined by the recess  70  may have any desired shape and it is shown as rectilinear solely by way of example. It could have curved walls. It could be circular or some other curvilinear shape. It could be non-symmetrical so that the corresponding insert  24  can be placed in the recess  70  in only one orientation. Extending downwardly from the bottom wall  90  of the recess  70  there are terminals  96  and  98 . 
     Referring now to FIGS. 1 through 11 the structure and arrangement of the contacts  16  and terminals  96  and  98  will be discussed in greater detail. The present invention is directed to a stacked connector  10  comprising a first receptacle  14  in a first portion  74  of the connector  10  and a second receptacle  16  stacked on the first receptacle  14  in the first portion of the connector  10 . A group  20  of first contacts  18  is arranged in the first receptacle  14  and a group  22  of second contacts  18  is arranged in the second receptacle  16 . A second portion  76  of the connector  10  is arranged adjacent to the first  14  and second  16  receptacles and includes the recess  70 , which extends behind the first  14  and second  16  receptacles for receiving an insert  24  containing at least one filtering circuit element which will be described in greater detail later. The groups  20  and  22  of first and second contacts  18  have extensions  66  and  68 , which extend into the second portion  78  of the connector  10 . The extensions  66  and  66  of the first and second groups  20  and  22  of contacts  18  are arranged along the top wall  88  of the recess  70 , preferably in single file fashion, for connection to the insert  24 . 
     As shown in FIGS. 3,  5  and  7  the lower group  22  of contacts  18  include a first section  58  which extends into the receptacle  14  and is supported by the flange  48  and the medial wall  82 . The extended section  66  of these contacts  18  first bends upwardly in the recess  70  until it generally reaches the top wall  88  and then it bends rearward along the top wall  88  of the recess  70  to form a first row  100  of contacts  18  for electrical connection as desired to the insert  24 . As shown in FIGS. 3,  6  and  8  the upper group  20  of contacts  18  also include a first section  58  which extends into the receptacle  16  and is supported by the flange  50  and the medial wall  82 . The extended section of these contacts  18  go generally straight into the recess  70  along the wall  88  to form part of the first row  100  of contacts  18 . In the first row  100  of contacts  18  the contacts from groups  20  and  22  alternate or are staggered within the row. 
     As shown in FIG. 1, in a particularly preferred embodiment the second group  22  of contacts  18  are arranged in the second receptacle  16  above the first group  20  of contacts  18  in the first receptacle and corresponding first group  20  and second group  22  of contacts  18  within the receptacles are aligned in a given plane. For example, contact  18 ′ in the second group  22  is arranged directly above contact  18 Δ in the first group  20  so that they lie in a common plane. As shown best in FIGS. 7 and 8, preferably the contacts  18  have a given width W 1  in their contactor section  58  and a narrower width W 2  in their extension sections  66  or  68 . The extension sections  68  of the first group  20  of contacts  18  are arranged along one side  102  of contacts  18 . The extension sections  66  of the second group  22  of contacts  18  are arranged along an opposing side  104  of the contacts  18 . This permits the extensions  68  or  66  of the respective first and second groups  20  or  22  of contacts  18  to extend substantially parallel to one another along the wall  88  of the recess without interference or electrical shorting. The present invention, however, contemplates that other methods of arranging the extensions  66 ,  68  of contacts  18  into single file could be used. 
     As shown in FIGS. 2,  3 ,  5 ,  6 ,  9 ,  10  and  11  a third group  106  of contacts  96  and  98  is arranged separately from the first  20  and second  22  groups of contacts  18  along a different wall  90  of the recess  70  for connection to the insert  24  and for connecting the stacked connector  10  to circuitry (not shown) external of the stacked connector  10  and the insert  24 . The extensions of the first and second groups  20  and  22  of contacts  18  are arranged in the top portion of the connector  10  along the wall  88  and the third group  106  of contacts  96  and  98  are arranged in a row  108  in the bottom portion of the connector  10  along wall  90 . The contacts  96  and  98  preferably alternate within the row  108 . A first mating portion  110  of the contacts  96  and  98  are supported in slots  120  in the bottom wall  90  and are arranged as a single second row of contacts  96  and  98  in the recess  70  along the bottom wall  90  of the recess. The contacts  96  and  98  include a second, or mounting portion  112  which are arranged in at least two substantially parallel rows  114  and  116  for electrical connection externally of the connector  10  to a printed wiring board, (not shown). Although shown as through hole-type terminations, other types of terminations (e.g. surface mount) could be used. 
     The first portion  110  of the contacts  96  and  98  are adapted for electrical connection to the insert  24  and the second portions  112  are adapted for connection to external circuitry. The portions  112  for external connection arranged in the first row  114  correspond to the contacts  18  in the first receptacle  14  and the terminal portions  112  in the second row  116  corresponding to the contacts  18  in the second receptacle  16 . Each of the terminals  98  for external connection in the first row  114  is preferably arranged in a common plane with a corresponding terminal  96  for external connection in the second row  116 . In the embodiment shown the terminals  96  for external connection in the second row  116  may include a bend portion  118  intermediate the first and second portions  110  and  112  of the contacts  96 . This permits the contacts  96  in the second row  116  to transition from a single row of contacts at the first portion  110  thereof to the substantially parallel rows  114  and  116  of contacts  96  and  98  at the second portions  112  thereof. 
     As shown in FIGS. 9,  10  and  11  the first portion  110  of the contacts  96  arid  98  have a “C” shape for snapping into the slots  120  in the bottom wall  90  of the housing  12 . They are held in place by the projection  122  at the free end of the contact portion  110  such as by friction. In contacts  96  the opposing end of the “C” shaped portion  110  at the bend  118  first bends generally perpendicularly to the “C” shaped portion in the plane of that portion. It then bends generally perpendicularly again in a plane generally normal to the plane of the “C” shaped portion  110 . Finally it bends once again generally perpendicularly to the plane of the sc bend and extends as the terminal portion  112  in a plane generally parallel to the plane of the “C” shaped portion  110 . The bend in the terminals  96  moves those terminals in row  116  behind the terminals  98  in the row  114  so that each of the terminals  96  in row  116  are arranged in a common plane with a corresponding terminal  98  in the other row  114 . The terminal portions  112  of terminals  96  extend from the inner end of the “C” shaped portion  110  opposed to the free end thereof. The terminal portions  112  of the terminals  98  extend from the leg of the “C” shaped portion  110  rearward of the terminals  96 . 
     In the most preferred embodiment as shown in FIGS. 2,  3  and  4  a filter insert  24  is provided in the recess  70 , which is electrically connected between the extensions  66  and  68  of the first and second groups  20  and  22  of contacts  18  arranged in the row  100  at the top wall  88  of the recess and the first portions  110  of the contacts  96  and  98  in the row  108  at the bottom wall  90  of the recess  70 , which are to be utilized in the circuitry connected by the connector. The insert  24  has a series of slots  124  at its top wall  126  which are adapted to receive the contact extensions  66  and  68  in the row  100  at the top wall  88  of the recess  70  and a second series of slots  128  at its bottom wall  130  which are adapted to receive the first portions  110  of the contacts/terminals  96  and  98  in the row  108  at the bottom wall  90  of the recess. 
     A filter circuit element or elements  132  such as common mode chokes are supported within the insert  24 . Other filtering elements known to those skilled in the art such as inductive serial filters, differential filters, low pass capacitive filters and other magnetic filters may be used. Conductors such as wires shown generally as  134  extend from the filter circuit  132  into the top slots  124  and bottom slots  128  of the insert for connecting the filtering circuit elements to the contact extensions  66  and  68  and the contact portions  110  of the contact  96  and  98 . The connection between the wires  134  and the respective contacts  66 ,  68 ,  96  and  98  may be made by any desired means, as for example, soldering, brazing, welding or by mechanical spring contact. The insert  24  can comprise a potted module wherein a polymer is molded about the filter circuit elements or it can comprise a hollow insert as shown wherein the filter circuit elements are supported with the insert  24 . The insert  24  in addition to its top  126  and bottom  130  walls further includes opposing side walls  136  and  138  connecting the top and bottom walls. It further includes a rear wall  140 . In the embodiment shown the insert has a box shape made up of these walls  126 ,  130 ,  136 ,  138  and  140 , however if desired it could be a fully enclosed box having a front wall (not shown). The filtering circuit elements can be supported within the insert  24  by any desired means. 
     It should be understood, the electrical circuit  132  is preferably a filter or the like, although it will be recognized that other electrical devices may be received in the insert  24  without departing from the spirit and scope of the present invention. For example, the electrical device may be a resistor or capacitor, a simple electronic circuit, an antenna, a complex integrated circuit, etc. 
     In particular, it is seen in FIG. 2 that the outer shield  26  includes a rear wall  40  which when bent into place behind the insert  24  completes the connector  10  and holds the insert  24  in place. Importantly, the aforementioned ground shield  26  is fitted over the housing  12  and insert  24  so that the rear wall  40  covers the rear portion of each contact  66 ,  68 ,  96  and  98 . It should be understood, the shield  26  is grounded or is to be grounded, and therefore it should not touch those contacts. The rear panel  40  of the shield  26  is preferably spaced from the rear portion of the housing  12  by a distance of about 1 mm, although greater spacing may be employed without departing from the spirit and scope of the present invention. 
     Referring now to FIGS. 12,  13  and  14  a brief description of exemplary filtering circuit diagrams that can be used within the insert  24  of a double deck universal serial bus connector will be described by way of example. There are, in general, three types of electrical diagrams represented in these Figs. 
     FIG. 12 illustrates a filtering circuit  132  that contains a common mode choke  142 . FIG. 13 shows a filtering circuit  132 ′ containing common mode chokes  142  in combination with isolation transformers  144 . FIG. 14 illustrates an electrical filtering circuit  132 ″ that contains other components for signal conditioning and electromagnetic interference reduction. In each Figure “A” represents one receptacle (e.g.  14 ), wile “B” represents the other receptacle (e.g.  16 ). Therefore, “A 1 ”, “A 2 ,” “A 3 ” and “A 4 ” represent the group (e.g.  20 ) of contacts  18  in one receptacle. Likewise, “B 1 ”, “B 2 ”, “B 3 ” and “B 4 ” represent the group (e.g.  22 ) of contacts  18  in the other receptacle. 
     The purposes of all the filtering circuits  132 ,  132 ′ and  132 ″ shown are: to reduce EMI (electromagnetic interference) and improve product safety and signal quality. The electrical and magnetic components are used to connect upper and lower portions of an exemplary double deck USB connector  10  to a printed circuit board (PCB). The electrical components can be used to achieve the stated purpose in both single-ended and differential transmission modes. Since the differential transmission is more common the following discussion focuses on the differential transmission applications. In a differential transmission mode a useful signal is transmitted using 2 wires (pair). 
     In the electrical diagram of FIG. 12 the EMI is reduced by introducing the serial impedance to a time variable signal. If a differential pair in the electrical circuit  132  is selected as A 2  and B 2 , then the wires are twisted together and threaded through a common inductor forming a common mode choke  142 . In such an arrangement the signal represented as a differential between voltages on the individual wires is not affected, but a common mode or parasitic voltage is attenuated proportionally to the properties of the common mode choke (magnetic permeability, number of turns and so on). The filtering circuit  132  provides inexpensive means to reduce EMI and is easily included in the insert  24 . 
     The filtering circuit  132 ′ of FIG. 13 provides a transformer  144  that isolates input (cable) from output (solder tails). This transformer  144  separates the dangerous high speed pulses that may damage equipment or become a safety risk to the user (lightning or ESD electrostatic discharge). In addition the transformer  144  is a low pass filter, i.e. the voltage changes on one transformer winding induce the corresponding voltage changes on another winding. However due to inductive properties the high frequency harmonics are attenuated by the transformer. The transformer  144  is also used simply to regulate the signal voltages as needed for signal processing. In some cases the transformers  144  are used to go from a signal ended (duplex) to a differential signaling. 
     The filtering circuit  132 Δ of FIG. 14 similar to FIG. 13 with an important difference that the circuit  132 Δ contains additional components or circuit elements. In the configuration shown resistors  146  are connected to central tabs  148  of the transformers  144 ′, and also all cable inputs are connected to a common ground through a high voltage capacitor  150 . The impedance of such a circuit  132 Δ is close to the impedance of the input cable so the reflections that are caused by impedance mismatch are reduced. In addition to that, the input wires  4 - 8  not used for signal transmission are terminated (connected to the ground), so that any voltage mode on these wires is prevented from radiating. The high voltage capacitors  150  isolate sensitive equipment from the discharges that may affect equipment through common ground. 
     The filtering circuits  132 , etc. presented in FIGS. 12-14 are merely illustrative and various other filtering circuit elements or other circuit designs could be employed in the insert  24 . The enlarged size of the insert  24  in accordance with this invention permits a larger number of circuit elements to be included in the insert circuitry, which provides a substantial improvement over prior approaches. The values for the various elements illustrated in FIGS. 12-14 may be selected as desired in accordance with conventional practice. 
     While the present invention has been described in connection with the embodiments of the various figures, it is to be understood that other similar embodiments may be used or modifications and additions, may be made to the described embodiment for performing the same function of the present invention without deviating therefrom. Therefore, the present invention should not be limited to any single embodiment, but rather construed in breadth and scope in accordance with the recitation of the appended claims.