Abstract:
A connector assembly that is mountable on a circuit board includes a casing having a metallic housing. The housing has at least one receptacle where a connecting element is mounted. A shielded cable connects between the connecting element and an interconnect that is attached to the casing. The interconnect has a plurality of contact elements adapted to contact the circuit board. The metallic housing can be fitted with any one of variously colored insulating shells either during manufacture or in the field. The shell can later be slidably removed and replaced, even after the housing was attached to a circuit board. The casings can have dovetail slots that mate with dovetail ridges on an insert used to attach the casings together.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to connector assemblies and assembly methods, and in particular, to devices that are adapted for various working environments. 
   2. Description of Related Art 
   Simple, reliable and effective connectors are needed in various electronic applications. Also, avoiding transmission losses and avoiding the receipt or transmission of electromagnetic interference (EMI) is important in many applications involving instrumentation, test equipment and high frequency applications handling signals such as video signals, shortwave signals, walkie-talkie signals, etc. 
   The problems with losses and EMI can be ameliorated with well-known shielding techniques, which include placing critical components inside a metal enclosure, and using shielded coaxial cables and shielded connectors that have a central lead surrounded by a cylindrical metal shell (for example, BNC or TNC connectors). In particular, coaxial shielded cables that have an impedance matching that of the source and destination tend to have little EMI problems or losses due to radiation, reflections or IR losses. 
   Applications employing multiple connectors can be especially vulnerable or prone to losses and EMI. Known compact connectors have placed a pair of connectors in a single assembly and routed wires attached to the rear of the connectors through a 90 degree turn in order to attach to contacts designed to connect to a printed circuit board. The radius of this 90 degree turn and the geometry of nearby metallic components greatly affect the losses and EMI effects, making manufacturing difficult. 
   Often, such connectors are mounted through a hole in a metal panel and held in place with a nut. In these cases it is often desirable to avoid multiple ground connections to such a panel in order to avoid ground loops that can be very sensitive to low-frequency interference from power mains. On the other hand, it is highly desirable to provide a high frequency ground on the panel in the vicinity of the connector to prevent the panel from acting like an antenna for the connector. For this reason, known connectors have employed a miniature capacitive element that connects between the connector&#39;s ground and the panel. For example, the capacitive element can be pressed against the connector by a metal strap or a shielding enclosure that reaches out to make contact with the back of the metal panel. 
   Accordingly, minimizing losses and EMI considerations place significant burdens on the manufacturers of electronic equipment who may need flexibility in arranging and efficiently placing connectors on printed circuit boards. These considerations also place significant burdens on the manufacturers of connectors who must be able to produce high-quality connectors efficiently and to develop standardized designs that can be adapted to various environments. Connector manufacturers would also like to work with castings and molds that can meet high-performance standards when necessary but can be configured to be cost-effective for less demanding environments. 
   In many electronic applications requiring multiple connectors, these connectors must be color-coded to help the end-users. Stocking a large number of variously colored connectors can be inefficient for manufacturers. Also, during manufacture or repair a wrongly colored connector may be inadvertently soldered onto a circuit board, which greatly increases the time required to complete manufacturing or repair. 
   In FIG. 2a of U.S. Pat. No. 6,042,394 the shield of cables 18 are shown adjacent to the shields 31 around each of the center contacts 15. The specification says (column 3, lines 57–58) the cables are intended to “meet impedance requirements or to avoid deteriorating reflections,” without describing how or if the shields are connected. 
   In U.S. Pat. No. 6,679,728 a pair of mini BNC connectors are formed with a common metal case 10 having a connected pair of shielding cylinders 101 and 102. Casing 10 is described as having insert legs 107. 
   In one embodiment of U.S. Pat. No. 5,169,343 the outer contact parts of a column of coaxial connectors are connected to shielding cases 22 and 23. Also, the rear wall 33 of casing 23 serves as the shield for two separate inner contacts in the column of coaxial connectors. Each of the casings 22 and 23 have a separate pair of mounting pins 24. In the embodiment of FIGS. 6 and 7 a column of coaxial connectors has a common shield formed of a single metal block 49/50. 
   In U.S. Pat. No. 5,730,621 a pair of BNC or TNC connectors are mounted in parallel in a plastic block containing shunting capacitors 5 and 5′. 
   In U.S. Patent Application Publication No. 2003/0073328 a motherboard can be connected to a daughterboard by an interconnection system that has a number of twin lead shielded cables. Each of the signal leads of each pair is fitted with a spring contact that engages contact pads on the circuit boards. While FIG. 1A shows a relatively open structure, the cables can be packaged inside a unitary housing as shown in FIG. 13A. 
   In U.S. Pat. No. 6,234,834 connector bodies 21, 22 and 23 are stacked and held together with dovetails 224 and 232. Each of the connector bodies have four contacts in each of the three contact groups 3. In addition, a common ground is provided by contact 4 which has three arms 44 that are inserted between the contacts of each of the three groups 3. The stack is mounted inside a conductive shield 1. See also U.S. Pat. No. 6,508,665. 
   In U.S. Pat. No. 5,863,222 a pair of connectors are mounted on a common header 20, each having a number of contact pins 21. The back of both connectors is shielded by a grounded plate 30 that is connected to a circuit board by the tabs 38. 
   In U.S. Pat. No. 4,806,107 a high frequency backplane connector has several rows of connectors separated by elements 41, 42. The connectors are mounted in housing 50 and flexible circuit board 27 inside the housing connects these connectors to the pins 61–63 that in turn connect to a printed circuit board. 
   In FIG. 1A of U.S. Pat. No. 6,244,896 a row of RJ connectors are mounted inside a common shield 2 that has ground tab 15 for engaging shields of RJ plugs. In the embodiment of FIG. 4 an upper and lower row of RJ connectors are stacked together. 
   See also U.S. Pat. Nos. 5,190,461; 5,085,590; 5,921,814; 6,626,700; and 6,022,245. 
   SUMMARY OF THE INVENTION 
   In accordance with the illustrative embodiments demonstrating features and advantages of the present invention, there is provided a connector assembly having a casing with a metallic housing that has at least one receptacle. The casing is adapted for mounting on a circuit board. Also included is at least one connecting element mounted at the at least one receptacle. The assembly also has an interconnect attached to the casing. The interconnect has a plurality of contact elements adapted to contact the circuit board. Also included is a shielded cable connected between the connecting element and the interconnect. 
   In accordance with another aspect of the invention a connector assembly is provided with a metallic housing adapted for mounting on a circuit board. The metallic housing has at least one receptacle. Also included is an insulating shell sized to fit around the metallic housing. The insulating shell is slidably removable from the metallic housing. The assembly also has at least one connecting element mounted at the at least one receptacle. Also included is an interconnect that is attached to the metallic housing and that has a plurality of contact elements adapted to contact the circuit board. At least one of the contact elements is coupled to the connecting element. 
   In accordance with another yet aspect of the invention a connector assembly is provided with a pair of metallic housings each adapted for mounting on a circuit board and each having at least one receptacle. The metallic housings each have a dovetail slot. Also included are connecting elements mounted at the at least one receptacle of each of the metallic housings. The assembly also includes an insert and a pair of interconnects each attached to a corresponding one of the housings. Each of the interconnects has a plurality of contact elements, at least one of them coupled to the connecting element of a corresponding one of the housings. The contact elements are attached to the housings and are adapted to contact the circuit board. The insert has on opposite sides dovetail ridges sized to slide into the dovetail slots of the metallic housings. Thus, by means of the dovetail ridges on the insert the housings can be attached together. 
   In accordance with another yet aspect of the invention a connector assembly method is provided employing a plurality of variously colored insulating shells and a metallic housing having a receptacle and contact elements. The method includes the step of bringing the metallic housing to the vicinity of a circuit board. Another step is selecting one of the variously colored insulating shells and fitting it around the metallic housing. The method also includes the step of connecting the contact elements to the circuit board. 
   By employing assemblies and assembly methods of the foregoing type an improved connection technique is achieved. In a preferred embodiment multiple connectors are provided on a single housing formed from a single metal casting. 
   For example, the cylindrical metal sleeves of a pair of BNC connectors are integrally cast with a common back frame that has an open rear recess. Thin tubular sockets with springy fingers are mounted in the cylindrical metal sleeves. These thin tubular sockets are surrounded with a tubular insulator, and are fastened in place by an annular spring clip. 
   The proximal ends of the tubular sockets are connected to the center leads of shielded coaxial cables. These coaxial cables are routed through a recess in the back of the metal housing to an interconnect in the form of a plastic carrier holding a number of pins designed to be soldered into a printed circuit board. In particular, the center lead and the shield of the coaxial cables are separately connected to individual pins of the interconnect. The coaxial cables can be easily installed and still maintain excellent loss and EMI characteristics. In particular, the coaxial cables can be routed through the recess without the need to place them in an exact position or to maintain a precise radius of curvature. High immunity to EMI can be achieved by covering the recess containing the coaxial cables with a metal backplate. 
   On the other hand, the foregoing metal housing can be fitted with ordinary wire leads instead of coaxial cables for applications that do not have strict requirements on avoiding losses or EMI. 
   The preferred metal housing can be adapted for an even greater variety of applications by casting it with a dovetail groove on opposite sides. Then multiple housings can be ganged together with an interconnecting insert having an opposing pair of dovetail ridges designed to fit into the dovetail grooves on the metal housings. The preferred insert is a plastic plate molded with dovetail ridges on opposite sides. 
   Preferably, a color-coded plastic shell would be slid over the metal housing either during manufacture or at the installation site. The shells are easily replaced in the event the wrong color coding was selected. Also, the plastic shell can be chosen to accommodate embodiments where the circuit board contacts emerge to the rear or to the side. In addition the shells can be formed with openings designed to accommodate capacitive elements or the above mentioned dovetail slots. These capacitive elements are preferably held in place by a metal bracket or enclosure that extends to touch the back of a metal panel to which the connector may be attached. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above brief description as well as other objects, features and advantages of the present invention will be more fully appreciated by reference to the following detailed description of presently preferred but nonetheless illustrative embodiments in accordance with the present invention when taken in conjunction with the accompanying drawings, wherein: 
       FIG. 1  is a side, cross-sectional view of a connector assembly in accordance with principles of the present invention; 
       FIG. 2  is a side view of the assembly of  FIG. 1 ; 
       FIG. 3  is a top view of the assembly of  FIG. 2 ; 
       FIG. 4  is a side view of the metal backplate in the assembly of  FIG. 1 ; 
       FIG. 5  is an side view of the metallic housing of  FIG. 1 ; 
       FIG. 6  is a rear view of the housing of  FIG. 5 ; 
       FIG. 7  is a bottom view of the housing of  FIG. 5 ; 
       FIG. 8  is an front view of the annular clip of  FIG. 1 ; 
       FIG. 9  is an end view of an insert that may be used to connect the housings of  FIG. 1  together in groups; 
       FIG. 10  is an assembly diagram associated with the components of  FIG. 1 ; 
       FIG. 11  is an exploded, perspective view of an assembly that is an alternate to that of  FIG. 1  and which is fitted with alternate leads; 
       FIG. 12  is an exploded perspective view of the assembly of  FIG. 11  with an insulating shell that is an alternate to that of  FIG. 1 ; 
       FIG. 13  is an exploded perspective view of a trio of matching assemblies as per  FIG. 12  that are attached together with a dovetailed insert; and 
       FIG. 14  is an exploded perspective view of a pair of matching assemblies as per  FIG. 12  that are attached together and fitted with additional components. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to  FIGS. 1–8 , a connector assembly is shown as a casing having a metallic housing  10  with an insulating shell  12 . The housing  10  is a zinc plated steel die casting with a rear rectangular block  14  and a pair of parallel cylindrical metal sleeves  16 , encompassing openings  18 , herein referred to as receptacles. Sleeves  16  are each shown with an opposing pair of stubs  16 A that are typically employed in BNC connectors, although it will be appreciated that the principles of the present invention can be applied to other types of connectors. Embedded in slots  17  in housing  10  are external grounding tabs  19 , shown herein as bifurcated stakes designed to snap into a hole in a printed circuit board  21  (shown in phantom). 
   Mounted in receptacles  18  are pair of connecting elements  20  having at their distal ends four springy, longitudinal fingers  22  distributed around a cavity  24 . The proximal ends of connecting elements  20  each have a wire hole  30 . The central lead  32  of shielded cable  34  is soldered into wire hole  30 . Molded around the junction between element  20  and cable  34  and locking onto flange  35  of element  22  is an insulating knob  36 , which has a pair of diametrically opposed, stepped grooves  38 . 
   Elements  20  have an annular barb  40  that allows insulating collars  42  to be pressed onto elements  20  into abutment with knobs  36 , but not withdrawn in the opposite direction. The collars  42  are made with a uniform internal diameter but the proximal end of the collar has an outside diameter that is greater than the outside diameter of the distal end. 
   The connecting elements  20  can be held in place with annular clips  60  having a flat transverse annulus  60 A with a pair of longitudinally extending arms having a section with an inward bight  60  that leads to a cylindrical section  60 C split with bifurcations  60 D. After clip  60  is placed around cable  34  and snapped into stepped grooves  38  of knob  36 , cables  34  can be inserted through the receptacles  18  and the cable tunnels  61  to allow the bifurcations  60 D to ride inwardly on one of the four splines  62  deep within receptacle  18 . The bifurcations  60 D are angled to allow insertion but resist withdrawal. The cables  34  may be previously fitted with contact elements  52 / 54  if they are small enough, otherwise these elements are installed after the cables routed through the tunnels  61 . In this embodiment the upper one of the cables  34  makes a simple downward turn, while the lower cable makes a more complicated pigtail turn. 
   Shielded cables  34  are conventional coaxial cables having the previously mentioned central leads  32  encircled by an insulating sleeve  44 , which is in turn surrounded by a coaxial shield  46  in the form of a copper braid covered by insulation  48 . In one embodiment the shielded cables  34  were able to carry signals of 2 GHz or more, and suitably rated for 3 Ghz signals. 
   The central leads  32  at the end of cables  34  opposite connecting elements are soldered into the hollow cylindrical barrels  50  that are integral with pins  52 , which are herein referred to as contact elements. As shown in  FIG. 10 , braid  46  is also soldered into the hollow barrel  51  of the contact elements  54 , which are identical to elements  50 / 52 . 
   Contact elements  52  and  54  are shown in  FIG. 10  molded into a carrier  56  and the elements inside carrier  56  are referred to herein as an interconnect. In some embodiments carrier  56  may be a plastic grid with apertures sized to hold elements  52  and  54 . In the embodiment of  FIG. 1  the contact elements forming an interconnect (only elements  52  are visible) are not held in the hollow  57  by a separate carrier but are held in place by virtue of the stiffness of cables  34 . In such an embodiment guideways or guiding ridges (not shown) in the assembly may keep the cables  34  and their braids  46  in approximately the correct position. Alternatively, the recess  58  containing cables  34  can be filled with a potting compound to hold in place the cables  34  and the contact elements  52 / 54  attached thereto. 
   Previously mentioned insulating shell  12  closely embraces the top, sides and bottom of the metallic housing  14  and its threaded barrels  12 A. Barrels  12 A of shell  12  cover about half the length of the metal sleeves  16  and are threaded so the assembly can be secured in a hole in a conductive panel  64  (shown in phantom) with a nut or other fastener (not shown). Shell  12  has a number of subjacent slots  66  giving clearance so that the shell can be slid onto or off the housing  14  without interference from pins  52 / 54  or stake  19 . 
   A pair of front feet  68  at the front corners of shell  12  and a pair of rear feet  70  at the rear corners raise the assembly off circuit board  21 , which can be important for flushing away residues that might otherwise accumulate under the assembly. As explained further hereinafter, this assembly can be assembled in such a way that the tubular sleeves  16  are perpendicular to the printed circuit board  21 , in which case feet  71  on shell  12  perform a similar function of lifting the assembly off the circuit board. 
   The block portion  14  of housing  10  has a cross wall  73  extending between a pair of parallel side walls  72  that flank an upper plateau  74  and lower plateau  76 , which plateaus are pierced by previously mentioned tunnels  61 . As shown in  FIG. 6 , a tubular portal  80  to the right of tunnel  61  on upper plateau  74  and tubular portal  82  to the left of tunnel  61  on plateau  76  constitute the openings to grounding holes that extends through the bulk of block portion  14 . 
   As shown in  FIG. 7  the far end of the grounding hole of portal  82  reaches a side aperture  84  that opens into a recess  85  of block  14  having a cylindrical hump  86  containing previously mentioned tunnel  61 . Another similar opening exists on the opposite side of block  14  for the grounding hole of portal  80 . As described further hereinafter, in some embodiments a lead can be inserted into the grounding hole of portal  82  (and portal  80 ) and routed to or through opening  84  where the lead can be bent or soldered to hold it in place. In fact, a lead  81  is shown in  FIG. 1  projecting from portal  80 , and making a downward turn in order to attach along with pins  52  into the printed circuit board  21 . 
   A ridge  88  ( FIG. 6 ) extending across plateau  74  meets a spaced pair of parallel ridges  90  on the insides of walls  72 . The overhang  96  ( FIG. 4 ) of metallic backplate  94  will rest on ridges  88  and  90 . Also the pins  98  on the inside of backplate  94  are inserted in the holes  92  of walls  72 . In addition, the inside face of backplate  94  has a raised region  100  with an outline designed to fit snugly between walls  72 . 
   Starting in an edge of walls  72  and running most of the length of housing block  14  are a pair of dovetail slots  99 . In  FIG. 9  insert  104  is shown having a center plate with a pair of opposing dovetail ridges  106  that give the insert a cruciform cross-section. The insert  104  is designed so that one of its dovetail ridges  106  can fit snugly into one of the dovetail slots  99  on housing block  14 . As described further hereinafter, the other dovetail ridge on insert  104  can slide into a dovetail slot on another assembly similar to the one shown in  FIG. 1 . Therefore, multiple assemblies can be stacked or ganged together. 
   Instead of the illustrated dovetailed inserts, alternative inserts may have ridges with a cross-section having a keyhole shape, hooked shape, etc. Also, the ridge need not be one continuous element but may be a number of spaced elements. Moreover, the ridge may snap into mating groove instead of sliding. In addition, some connector assemblies may be formed with a ridge on one side and a slot on the other side so that they can be attached together without the need for a separate insert. 
   Located near the lower rear corner on opposite sides of housing block  14  are locking stubs  97 , which are tapered so that when shell  12  is slid over housing  10  stubs  97  can enter and lock into apertures  95  in shell  12 . Shell  12  also has a pair of slots  112  allowing easy access to the dovetail slot  99  in housing block  14 . Shell  12  also has an optional aperture  114  designed to hold a capacitive element that will be described presently. 
   Referring to the alternate embodiment of  FIG. 11 , components corresponding to those previously illustrated in  FIG. 1  will have the same reference numeral but increased by 200. In particular, metallic housing  210  has a rectangular block  214  supporting an integral pair of sleeves  216  with locking stubs  216 A. The interiors of sleeves  216  communicate to the two openings  320  in the rear of block  214 . Attached to the bottom of housing block  214  are a pair of grounding tabs  219  designed to lock into holes on a printed circuit board (not shown). Locking stub  297  at the four back corners of housing block  214  serve the same function as the previously mentioned stubs (stubs  97  of  FIG. 5 ). Housing block  214  also has a wire portal  280  for receiving a grounding wire  281 . 
   A pair of plastic insulating collars  242  are designed to fit into sleeves  216  and extend back to the openings  320  in housing block  214 . Collars  242  have coaxial bores designed to receive connecting elements  220 , which are very similar to the previously described connecting elements (elements  20  of  FIG. 1 ), except that the rear portions of elements  220  have a simple integral wire lead  220 A. 
   Referring to  FIG. 12 , metallic housing  210  is shown assembled with insulating collars  242  mounted inside sleeves  216  and housing block  214 . Previously mentioned wire leads  220 A and grounding wire  281  are bent down and trimmed to extend below the bottom of housing block  214  an amount sufficient to allow connection to a printed circuit board (not shown). 
   An insulating shell  212  with a pair of threaded barrels  212 A is designed to slide over metallic housing  210  and lock into place when stubs  297  snap into holes  295 . In this embodiment there are no dovetail slots on housing block  214 . Instead, a pair of dovetail slots  322  serving the same purpose are formed on opposite sides of shell  212 . 
   Referring to  FIG. 13 , three identical sets of the components of  FIG. 12  are shown assembled but with differently configured wire leads  220 A′ and grounding wire  281 ′. Specifically, leads  220 A′ and wire  281 ′ are not bent and extend rearwardly an amount sufficient to allow connection to a printed circuit (not shown). In contrast to the embodiment of  FIG. 12 , the connector sleeves  216  will be oriented perpendicular to the circuit board. 
   The three illustrated identical assemblies are attached together with inserts  324  having a “butterfly” cross-section, that is, an opposing pair of dovetail ridges designed to fit into the dovetail slots  322  on the sides of shells  212 . 
   Referring to  FIG. 14 , the components shown in  FIG. 12  have been modified, paired, and attached together as a pair by means of previously mentioned insert  324 . In this embodiment, one of the leads  220 A has been fitted with an insulating sleeve  326 . Also, another grounding wire  281 A has been attached to housing block  214  to supplement the other grounding wire  281 . A metallic backplate  342  sized to fit inside the rear opening a shell  212 ′ provides enhanced shielding. 
   Also, in comparison to the previously mentioned shell (shell  212  of  FIGS. 12 and 13 ) an aperture  328  has been formed in the side of shell  212 ′ to receive a capacitive element  330 . When slid over sleeves  216  and shell  212 ′, the sheet metal structure  332  is capacitively coupled through element  330  to the metallic housing block  214 . Thus, if the assembly is then fastened onto a metal panel (not shown) by threading a nut onto threaded sleeves  212 A′, the metal panel will touch structure  332  and thus have a local high frequency ground connection through capacitive element  330  through housing block  214  and ground wires  281  and  281 A. 
   In some embodiments structure  332  may be replaced with a metal strap structure  334  having lips  336  designed to snap into slots  338  on the top and bottom of shell  212 ′. Strap structure  334  also has a trio of springy arms  340  that reach around to the front of shell  212 ′ in order to electrically contact a metal panel (not shown) to which the assembly may be attached as described before. 
   To facilitate an understanding of the principles associated with the foregoing apparatus, the assembly and operation of the connector of  FIGS. 1–9  will be briefly described, although it will be appreciated that the description for the other embodiments will be similar. 
   The cable  34  can be soldered to connecting element  20  before forming knob  36  around the soldered joint, as shown in  FIG. 10 . Thereafter, insulating collar  42  can be forced onto connecting element  20 , moving into abutment with knob  36  as annular ridge  40  is wedged and locked into the collar. The annular clip  60  can be slid onto cable  34  and pushed over knob  36  until bights  60 B snap into slots  38 . In some embodiments metal clip  60  will contact braided shield  46  of cable  34 , in which case the distal end of the shield will be grounded to the housing  10 , although in most embodiments such a grounding connection will not be made through clip  60 . Cable  34  can then be inserted through receptacle  18  ( FIG. 1 ) and through tunnel  61  until clip  60  reaches the illustrated position wherein bifurcated arm portion  60 C is wedged in place deep within receptacle  18 . 
   The unconnected ends of the center lead  32  and braid  46  of cable  34  can be soldered into the barrels  50  and  51  of the contact elements  52  and  54 , as shown in  FIG. 10 . If desired, carrier  56  can be molded around these contact elements, although in some embodiments these contact elements will maintain a desired position due to the restricted space existing in recess  58  ( FIG. 1 ). 
   In addition, ground wires can be inserted into portals  80  and  82 . The tip of the inserted wire can be held in place by being bent or soldered through an associated opening, such as opening  84 . The installed ground wires can be bent down. 
   Thereafter, shell  12  can be slid over metal sleeves  16  and into the position shown in  FIG. 1 . Slots  66  on the bottom of shell  12  avoid interference with pins  52  and  54 , wire  81  and stake  19 . The back of shell  12  can be closed by pressing cover  94  in place so that overhang  96  rests on ridges  88  and  90 , and pins  98  fit into holes  92 . 
   The connector assembly can be initially secured to the printed circuit board  21  by pressing stake  19  through a hole in the circuit board  21 . Simultaneously, pins  52  and  54  and the previously mentioned ground wires (for example ground wire  81 ) will also be inserted through corresponding holes in the circuit board  21 . These components inserted into circuit board  21  can then be soldered using conventional techniques such as flows soldering. 
   The circuit board  21  may be assembled so that it is adjacent to a metal panel  64  ( FIG. 1 ) which may be designed with openings through which sleeves  16  and threaded barrel  12 A are inserted. The panel openings may have flat portions that match the flats  12 B on threaded barrels  12 A. 
   An end user can use the illustrated connector by attaching a mating connector (for example, an unillustrated BNC connector) that has a center pin that fits between the fingers  22  of connecting element  20 . This mating connector will also have an outer female shell that fits around metal sleeve  16  and locks onto stubs  16 A. 
   High frequency signals can be conveyed through the illustrated connector. Shielded coaxial cables  34  will have an impedance that matches the impedance of devices attached to the connector to avoid reflections and losses. Cables  34  will maintain good transmission characteristics including low EMI that will not be appreciably degraded by the cable positioning or by the fact that the cables make sharp turns. In particular, the lower cable  34  of  FIG. 1  will make a tight pigtail turn, but this tight turn will not significantly degrade the cable&#39;s performance. 
   In some instances it will be desirable to color-code shell  12  so a user can quickly identify different connectors. Still, in some cases the connector assembly of  FIG. 1  will be installed with an incorrectly colored shell  12 . Nevertheless, shell  12  can be pushed off metal housing  10  by prying the sides of the shell clear of locking stub  97 . The slots  66  will provide clearance so that pins  52  and  54  and stake  19  will not prevent removal of shell  12 . The replacement shell can be installed simply by slipping it over housing  10  and locking the shell on stubs  97 . 
   It will be appreciated that metal housing  10  need hot be fitted with shielded cables and instead, simple insulated (or uninsulated) wires can be routed from cavity  30  of element  20  through tunnel  61  and into the barrels  50  of the contact element. In such designs care must be taken to bend the wire with a radius of curvature that avoids losses, radiation, and reflection, but this requirement may not be very demanding in low-frequency applications. 
   It will also be appreciated that metal housing  10  need not be oriented as shown in  FIG. 1  but may instead use leads that leave tunnel  61  without bending so that sleeves  16  are perpendicular to circuit board  21  as with the embodiment of  FIG. 13 . 
   It will further be appreciated that the connector assembly of  FIG. 1  can be mated with an identical assembly by using the insert  104  of  FIG. 9 . Having a central plate, insert  104  engages a relatively wide region to prevent rocking of the adjacent connector assemblies. 
   It will be appreciated that various modifications may be implemented with respect to the above described, preferred embodiments. While the illustrated metal housings are cast to provide a pair of connectors, other embodiments may provide more connectors or just a single connector. While external connectors are secured to the illustrated connectors by stubs on the metal sleeves, other connectors may be secured by threading, bayonet fittings, force fitting, etc. The illustrated insulating shell is optional as is the capacitive element, metal backplate, grounding wire etc. The connectors can be mounted on printed circuit boards or other circuit boards in which the connections may be made by wire wrapping, screw terminals, by receiving a pin previously mounted on the circuit board into sockets on the connector assembly, etc. Also, the size, shape and other dimensions of the connector can be varied depending on the desired strength, power rating, frequency rating, etc. 
   Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.