Abstract:
A modular cross-connect includes a chassis configured to receive a plurality of cross-connect modules therein and having a front face and a rear cover. A plurality of fixed portions of cross-connect modules are mounted in the chassis such that rear facing connectors of each of the fixed portions extend outward from the rear cover of the chassis. Each fixed portion has a front-facing connector configured to mate with a rear-facing connector of a corresponding removable portion of a cross-connect module. A plurality of reversible slots are formed in the chassis. Each slot is configured to receive a removable portion of a cross-connect module and to align a rear-facing connector of a removable portion of a cross-connect module for connection with a front-facing connector of a fixed portion of a cross-connect module. A plurality of doors are at the front face of the chassis, each door corresponding to one of the plurality of slots and being pivotally mounted for rotation about an axis parallel to a width of the chassis. Insertion of a removable portion of a cross-connect module into one of the plurality of slots causes a corresponding one of the plurality of doors to pivot about the axis to permit entry of the removable portion of the cross-connect module into the chassis.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a modular cross-connect used for routing, monitoring and testing of signals in, for example, the telecommunications industry. 
     2. Related Art 
     Digital signal cross-connect (DSX) equipment plays an important part in the installation, monitoring, testing, restoring, and repairing of digital communications networks. Digital signal cross-connect modules are often used to provide cross-connections of digital signal lines at locations that are suited for testing and repairing the digital lines. For instance, many telephone service providers&#39; central offices have digital signal cross-connect modules. A single DSX module generally interconnects two telecommunications apparatuses of a telecommunications network. The module is typically mounted in a rack or bank with similar modules. The bank forms a digital signal cross-connect unit (DSX unit). The DSX modules provide a point of access to the digital signals being transmitted over the digital lines of the telecommunications network, yet appear as almost invisible to the rest of the network. By utilizing the DSX modules, an operator can monitor, test and repair the digital equipment that is used by the telecommunications network without significantly interfering with the transmission of signals. 
     A need exists in the industry for low cost DSX chassis that have high density of modules. 
     BRIEF SUMMARY OF THE INVENTION 
     Accordingly, the present invention is directed to a modular cross connect with a removable switch assembly that substantially obviates one or more of the problems and disadvantages of the related art. 
     There is provided a modular cross-connect including a chassis configured to receive a plurality of cross-connect modules therein and having a front face and a rear cover. A plurality of fixed portions of cross-connect modules are mounted in the chassis such that rear facing connectors of each of the fixed portions extend outward from the rear cover of the chassis. Each fixed portion has a front-facing connector configured to mate with a rear-facing connector of a corresponding removable portion of a cross-connect module. 
     A plurality of slots are formed in the chassis. Each slot is configured to receive a removable portion of a cross-connect module and to align a rear-facing connector of a removable portion of a cross-connect module for connection with a front-facing connector of a fixed portion of a cross-connect module. A plurality of doors are at the front face of the chassis, each door corresponding to one of the plurality of slots and being pivotally mounted for rotation about an axis parallel to a width of the chassis. Insertion of a removable portion of a cross-connect module into one of the plurality of slots causes a corresponding one of the plurality of doors to pivot about the axis to permit entry of the removable portion of the cross-connect module into the chassis. 
     In a further aspect of the invention the doors each include a rail for guiding the module during insertion, doors are mounted on a horizontally mounted rod extending in a direction perpendicular to direction of insertion. 
     In a further aspect of the invention each module includes a release lever and a locking tab for coupling to a corresponding door. 
     In a further aspect of the invention a rail plate with grooves is added for guiding the modules during insertion. 
     In a further aspect of the invention a plurality of printed circuit boards are coupled to the connectors on the rear cover and aligned parallel to a direction of insertion of the modules. 
     In a further aspect of the invention each module includes two release levers and two locking tabs for coupling to a corresponding door and to a rail plate mounted over the bottom plate. 
     In a further aspect of the invention the modules may be inserted in two different orientations. 
     In a further aspect of the invention there is included a connector on the printed circuit board for engaging the module when the module is inserted, the connector having a chamfered edge. The connector may be a multi-pin make-before-break connector. 
     In a further aspect of the invention the top housing assembly of the chassis includes a Printed Circuit Board assembly with a plurality of switches, each of the switches having an LED integrally mounted within it. In a further aspect of the invention each module includes a micro-strip line PCB. The Printed Circuit Board assembly includes a micro-strip line PCB. 
     In a further aspect of the invention each switch includes a removable lense over the LED. 
     In a further aspect of the invention the module includes a plurality of jacks on its front side, each jack including a strain relief. 
     Additional features and advantages of the invention will be set forth in the description that follows, and in part will be apparent from the description, or may be learned by practice of the invention. The advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
    
    
     BRIEF DESCRIPTION OF THE FIGURES 
     The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. In the drawings: 
     FIG. 1 is a front isometric view of one embodiment of a cross-connect chassis of the present invention. 
     FIG. 2 is a rear isometric view of one embodiment of the chassis of the present invention. 
     FIG. 3 is an isometric assembly view of an cross-connect module of one embodiment of the present invention. 
     FIG. 4 is a partial cross-sectional view of a chassis and one inserted cross-connect module of one embodiment of the present invention. 
     FIGS. 5A-5E show different views of a cross-connect module of one embodiment of the present invention. 
     FIG. 5F shows a partial plan view of a printed circuit board (PCB) of a fixed portion mated to a printed circuit board of a removable portion of the cross-connect module. 
     FIGS. 6A-6C illustrate three different views of a fixed PCB assembly portion of one embodiment of the present invention. 
     FIGS. 7A-7C illustrate the printed circuit board of an insertion module of one embodiment of the present invention. 
     FIG. 8 illustrates a top housing assembly of the chassis of one embodiment of the present invention. 
     FIG. 9 illustrates a cross-sectional view of the top housing assembly. 
     FIG. 10 illustrates an isometric view of a PCB assembly portion of the top housing assembly. 
     FIG. 11 shows an isometric view of a rail plate of one embodiment of the present invention. 
     FIG. 12 illustrates additional detail of a door of one embodiment of the present invention. 
     FIG. 13 illustrates how multiple doors are assembled in the chassis. 
     FIG. 14 illustrates a cross-section of a make-before-break connector. 
     FIG. 15 shows an electrical schematic of tracer circuitry of the chassis. 
     FIGS. 16-17 illustrate electrical schematics of connections between the cross-connect modules and chassis in two different insertion orientations. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. 
     One embodiment of a cross-connect of the present invention is described with reference to FIGS. 1-14. 
     FIG. 1 is a front isometric view of a chassis  101  that receives a plurality of modules  120 . Three cross-connect modules  120 A- 120 C are depicted for purposes of illustration. Each module  120  is inserted into an interior space of chassis  101 . Sides of chassis  101  include a left side panel  180  and a right side panel  190 . Chassis  101  also includes a top housing assembly  125 , left and right side panels  180 ,  190 , a bottom plate  126 , a plurality of spacers  127 , and a plurality of doors  128 , which are shown in a closed position in FIG.  1 . Doors  128  are closed when modules  120  are removed to minimize the amount of dust and other debris that may enter the interior of chassis  101 . FIG. 1 also shows push buttons  110 , with internal LEDs. 
     FIG. 2 is a rear isometric view of chassis  101 . A back wall (rear cover)  140  of chassis  101  has a plurality of circular openings. When module  120  is positioned in chassis  101 , BNC jacks  220  extending from a rear portion of module  120  extend outward from corresponding openings in back wall  140 . Each BNC jack  220  is preferably secured in position in an opening of back wall  140  by a nut  490  (not shown in FIG. 2, see FIG. 4) that mates with a threaded portion on the body of jack BNC  220 . This also secures the rear portion (discussed below) of module  120  in chassis  101 . 
     As further shown in FIG. 2, chassis  110  includes left side panel  180  and right side panel  190 . Top housing assembly  125  includes a terminal block  215 , LEDs  210 , and tracer ports  230 . 
     Chassis  101 , as shown in FIGS. 1 and 2, includes top housing assembly  125 , side panels  180 ,  190 , bottom plate  126 , and rear cover  140 . Rear cover  140  is also used as a dust cover and a platform to securely mount the rear portion of modules  120 . Top housing assembly  125  is used for mounting switches  110 , tracer lights  230 , and power wiring. Bottom plate  126  is used as a platform to mount and support rail plate  101  (see FIG.  11 ). 
     FIG. 4 is a side or end cross-sectional view of chassis  101  illustrating positioning of module  120  within chassis  101 . This view illustrates that module  120  includes a fixed (or rear) portion  440  (rear PCB assembly  440 ) and a removable (or front) portion  480  (also called a switch PCB assembly). 
     Removable portion  480  is electrically connected to fixed portion  440  by an edge connector  460  (a multi-pin connector). Edge connector  460  of fixed portion  440  mates with an edge of a printed circuit board (PCB)  310  of removable portion  480 . Edge connector  460  preferably has chamfer edges and nickel/gold plating to improve reliability by reducing wear during insertion to and withdrawal from rear PCB assembly  440 . 
     Printed circuit board  310  of removable portion  480  mates with rear PCB assembly  440 . Side panel  180  is shown at the bottom of the assembly in FIG.  4 . An upper support bar  419  is shown at the top of the assembly. A rail  416  of rail plate  1101  at bottom is used to guide insertion of module  120 . FIG. 4 also shows a cross-section of top housing assembly  125 , terminal block  215 , and a cross-section of bottom support plate  126 . As illustrated, top housing assembly  125  includes push button switch  110  tracer port  230 , and rear LED  210 . 
     Rear PCB assembly  440  includes 4 edge-mount BNC jacks  220 , a PCB board  430 , and a make-before-break edge connector  460 . Microstrip line techniques are used on the board design to control the impedance of the conductors to achieve optimum RF parameters. An input signal normally enters at BNC “IN” jack  220 A, moves through a micro-strip line on one side of board  430 , loops through multi-pin connector  460 , moves through a micro-strip line on the other side of PCB  430 , and exits at BNC “XIN” jack  220 C. The signal paths are similar for “OUT” and “XOUT.” Specifically, an output signal normally enters through BNC “XOUT” jack  220 D, moves through a micro-strip line on one side of board  430 , loops through multi-pin connector  460 , moves through a micro strip line on the other side of board  430 , and exits at BNC “OUT” jack  220 B. (See also circuit diagram of FIG. 15, which shows an electrical schematic of tracer circuitry of chassis  101 , and FIGS. 16-17, which show electrical schematics of module  120  and chassis  101  in two different insertion orientations.) 
     When module  120  is inserted and mates with rear PCB assembly  440 , contacts of multi-pin edge connector  460  are forced open and the signal moves to PCB  310  then back to the rear PCB  430  before leaving chassis  101 . Thus, module  120  allows the user to monitor the signals and re-route them if necessary. 
     FIG. 3 shows an exploded, isometric view of removable portion  480  of module  120 . As shown in FIG. 3, module  120  includes a thermoplastic housing (frame)  305 , a thermoplastic lid  301 , and a printed circuit board (PCB)  310  that includes four mini-WECo jacks  302 . PCB  310  is enclosed within thermoplastic housing  305  and thermoplastic lid  301 . FIG. 3 also shows two locking release levers  303 ,  304 , which are used to disengage module  120  from chassis  101  upon withdrawal. 
     FIGS. 5A-5B show two views of removable module  120 . Module  120  includes housing (frame)  305  having PCB  310  mounted therein. (Several views of PCB  310  are also shown in FIGS. 7A-7C.) PCB  310  includes a portion  506  configured for mating with edge connector  460  of fixed portion  440 . Four MiniWECo jacks  302  are mounted on a front edge of PCB  310 . Micro-strip conductors on PCB  310  carry electrical signals from portion  506  to jacks  302 . A first switch assembly  505 A normally connects the conductors of jacks  302 B and contact post  517 A. A second switch assembly  505 B normally connects the conductors of jacks  302 C and contact post  571 B. Switch  505 A is connected to contact post  517 B (breaking the normal connection) upon insertion of a MiniWECo plug into jack  302 B. Similarly, switch  505 B is connected to  571 A (breaking the normal connection) upon insertion of a MiniWECo plug into jack  302 C.  302 A and  302 D are for monitoring purposes. FIG. 5B also shows a view of actuator  516  and contact post  517 , which are positioned towards the front of module  120 . 
     FIGS. 5C-5E show additional views of module  120 . Specifically, FIGS. 5C and 5E shows two side views of module  120 , and FIG. 5D shows module  120  with thermoplastic lid  301  mounted and closed. 
     FIG. 5F shows another partial view of module  120  that is mated with rear PCB assembly  440 . Rear PCB assembly  440  includes micro-strip line PCB  430 , BNC jacks  220  coupled to PCB  430 , and edge connector  460 . Removable portion  480 , which is mated with rear PCB assembly  440 , includes, as also shown in previous figures, PCB  310 , mini-WECo jacks  302 , and actuator  516 . Module  120  also includes a rail ridge (see also FIG. 12, element  1201 ) at the top, locking release levers  303 ,  304  and locking tabs  531 . Each mini-WECo jack  302  also has a strain relief ridge  533 , for improved product reliability. Strain relief ridge  533  is designed to minimize the insertion forces imposed on solder joint between the mini-WECo jack  302  and PCB assembly  440 . When a plug is inserted into the mini-WECo jack  302 , the strain relief ridge  533  will absorb and distribute the forces from the insertion onto the thermoplastic housing  305  and the thermoplastic lid  301 , with which it is in direct contact, and then transfer the insertion forces onto the chassis  101  (rather than onto the PCB  310 ). This can prevent solder joint fracture that will eventually degrade performance of chassis  101 . 
     Referring to FIGS. 4,  5 A and  5 C, fixed portion  440  is described in further detail. Fixed portion  440  includes PCB  430  upon which BNC jacks  220  are mounted at one edge. Edge connector  460  is mounted on an opposite edge of PCB  430 . Microstrip conductors on PCB  430  electrically connect BNC jacks  220  to edge connector  460 . Edge connector  460  makes connections between the conductors so that jack  220 A is normally connected to jack  220 C, and jack  220 B is normally connected to jack  220 D, to provide cross-connect functionality. However, when removable portion  480  is mated with edge connector  460 , the normal connections made by edge connector  460  are broken and the conductors are instead electrically connected to conductors within removable portion  480 . 
     FIGS. 6A-6C illustrate additional views of fixed portion  440  of module  120 . Specifically, FIG. 6A illustrates a front view of fixed portion  440  (i.e., looking into chassis  101  through open door  128 ), FIG. 6B illustrates a side view of fixed portion  440 , and FIG. 6C illustrates a back view of fixed portion  440 , looking from the rear of chassis  101  towards BNC jacks  220 . 
     FIGS. 7A-7C illustrate three additional views of printed circuit board  310  of removable portion  480 . Specifically, FIG. 7A shows a view looking into chassis  101  from the front, illustrating mini-WECo jacks  302  and a cross-section of PCB  310 . FIG. 7B illustrates a side view (i.e., looking at PCB  310  from a direction of right side panel  190 ), and FIG. 7C shows a rear view of PCB  310 . Note in particular mini-WECo jacks  302  and their stress relief ridges  533  in FIG.  7 B. 
     FIGS. 8 and 9 illustrate top housing assembly  125  that forms the top portion of chassis  101 . Top housing assembly  125  includes a chassis member  801  having a portion  803  that forms a top face of chassis  101 , a portion  805  that forms part of the front face of chassis  101  and a portion  804  that forms part of the rear face of chassis  101 . Switches  110  are structurally mounted on a PCB assembly portion  805 . LEDs  210  and tracer ports  230  are mounted on portion  804 . Switches  110  are electrically connected to a PCB  807 . LEDs  210  and tracer ports  230  are electrically connected to PCB assembly  807  via wires (not shown). PCB assembly  807 , terminal block  215 , LEDs  210 , tracer ports  230  and switches  110  constitute tracing circuitry that has no electrical interconnection to modules  120 . Configuration and operation of tracer circuitry would be apparent to a person skilled in the relevant art, and is illustrated in schematic form in FIG. 15, and FIGS. 16-17, which show electrical schematics of module  120  and chassis  101  in two different insertion orientations. 
     The PCB assembly  807  includes a PCB with pre-installed surface mount resistors and diodes (not shown in the figures), and push-button switch assemblies that include switch bodies  110 , removable/replaceable color lenses, and LEDs (not shown, housed inside switch  110 ). 
     FIG. 10 illustrates an additional view of PCB assembly  807 . As shown in FIG. 10, PCB assembly  807  includes a plurality of switches  110 , each of which includes an LED mounted integrally within it. Each switch  110  also includes a color-coded lens  1001 , which may be easily replaced in the field. 
     FIG. 11 is an illustration of a thermoplastic rail plate  1101 , which is mounted above bottom plate  126  in chassis  101 , and is used to guide modules  120  being inserted into chassis  101 . As shown in FIG. 11, rail plate  1101  includes rail grooves  1102 , rails  416 , spacer stabilizers  1103  to keep spacers  127  from moving after installation, and locking stoppers  1104  that mate with tabs  531  for guiding and fixing in place modules  120 . 
     FIG. 12 illustrates three views of door  128 , which upon insertion of module  120 , also functions as a rail guide. As shown in FIG. 12, door  128  includes upper rail ridges  1201 , a lock stopper  1202 , a hole  1203 , and a cavity  1204  for mating with corresponding parts of module  120 . Dashed line  1205  shows an axis of rotation of door  128  upon insertion of module  120 . 
     FIG. 13 illustrates additional detail of a door assembly  1305 , which is mounted on the front of chassis  101 . As shown in FIG. 13, door assembly  1305  includes a plurality of doors  128 , separated by spacers  127 . On either side of door assembly  1305 , there are end spacers  1304 . For each door  128 , a spring  1302  acts to keep it biased towards a closed state, to prevent entry of dust and other debris. A bracket  1301  is used to couple springs  1302  to door assembly  1305 . A circular rod  1303  is used to mount the springs  1302  and to link all doors  128  and spacers  127  together. End spacers  1304  and spacers  127  may be formed, for example, from metal or thermoplastic. 
     Door  128  is normally in a closed position until module  120  is inserted to open it Then door  128  serves as an upper rail, in addition to rail plate  1101 , to guide module  120  to mating correctly with the multi-pin connector  460  of rear PCB assembly  440 . Upon withdrawal of module  120 , spring  1302  will force door  128  back to a closed position. Thus, door  128  prevents dust and other debris from entering the interior of chassis  101  and causing contamination to internal components. As compared to a side-mounted door assembly, the vertical door design allows higher module density with the same chassis size, e.g., either 19″ or 23″ wide chassis. 
     FIG. 14 shows a cross-section of connector  460 . The connector shown in FIG. 14 is a make-before-break type connector. Connector  460  may also be a pin-and-socket type, which may be more reliable, and provide better performance, but would result in higher cost. 
     In operation, when removable portion  480  is coupled to fixed portion  440  via edge connector  460 , the electrical connections creating the cross-connect that were previously made by edge connector  460  (e.g., contacts  1402 ,  1403 ) are instead made by switches  505 A and  505 B. That is, when edge  506  of PCB  310  is inserted into cavity  1401  of connector  460 , contacts  1402 ,  1403  are forced apart, breaking the electrical connection between conductors  1404  and  1405 . This permits the signals from BNC jacks  220  and the connections made therebetween to be accessible at the front of removable portion  480 . (See FIGS. 16-17.) 
     Referring back to FIGS. 1 and 2, chassis  101  populated with modules  120  can be used in a telephone company central office to connect telephone company equipment. In this environment, the equipment is connected to BNC jacks  220  at the rear of chassis  101 . The fixed portions  440  then provide the desired interconnections between the equipment To reduce cost, modules  120  will not be needed until signal access is desired for re-routing or monitoring. Accordingly, it is anticipated that chassis  101  will typically be configured with all of fixed portions  440  in position in chassis  101  prior to chassis  101  being shipped to a customer. Modules  120  can then be added or removed by a customer, as necessary. 
     Referring back to FIG. 1, note that chassis  101  includes a row of lighted, push-button switches  110  along the top edge of the front panel. One switch  110  corresponds to each module slot of chassis  101 . Referring to FIG. 2, note that at the rear of chassis  101 , there is row of tracer ports  230  and a row of tracer LEDs  210 . A pair of tracer ports  230  and an LED  210  are also associated with each module slot of chassis  101 . 
     Switches  110 , ports  230  and LEDs  210  are used for troubleshooting cable runs by tracing cabling between equipment bays as is known in the art. For example, given a coaxial cable that connects a first module in a first chassis to a module in a second, remotely-located chassis, a tracer port  230  corresponding to the first module would typically be connected by a wire to a tracer port on the second, remotely-located module. Depressing switch  110  associated with the first module would then complete an electrical circuit that would (1) light an LED within switch  110  itself, (2) light rear panel LED  210  associated with the first module, and (3) light the remotely-located, rear panel LED associated with the second module. This facilitates the tracing of cabling by technicians for troubleshooting. 
     DSX chassis  101  of the present invention with cross-connect modules  120  installed provides signal crossing functions in digital networks located in a central cross connecting location for the ease of testing, monitoring, restoring and repairing the digital signals and associated equipment. Chassis  101  with BNC jacks  220  of fixed portions  440  preinstalled into chassis  101  can provide only crossing function capability. However, chassis  101  with removable module  120  installed can provide capabilities for testing, monitoring, and rerouting the digital signals as well as providing the normal crossing functionality. 
     Note that, when installed in a first orientation, module  120  permits front-panel access to the following signals: IN, OUT, MONITOR IN and MONITOR OUT. However, if module  210  is installed in a different orientation (i.e., rotated 180 degrees so that the MiniWECo jack  302  that was on the top is on the bottom after rotation), removable portion  480  permits front-panel access to the following signals: XIN, XOUT, MONITOR XIN and MONITOR XOUT. (See also electrical schematics of FIGS. 16-17.) This feature permits front panel access to all back-panel signals. Furthermore, signal access is achieved in a module size that is smaller that would be required to provide simultaneous access to back-panel signals, permitting a size savings in module  120  and chassis  101 . 
     It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined in the appended claims. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.