Abstract:
This invention relates to a subrack device applicable for an SDH network, and more particularly to a subrack device which can be produced flexibly in response to a customer&#39;s need. The subrack device has a subrack body commonly used regardless of a type of the subrack device. The subrack body has a circuit-board-unit housing portion and an outer-connecting-board mounting portion. Circuit boards and outer-connecting-board connecting-boards of different types are prepared. The outer-connecting-board mounting portion has a plurality of outer-connecting-board mounting territories. The outer-connecting-boards are plugged in the outer-connecting-board mounting territories to produce the subrack device meeting the customer&#39;s need.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to a subrack device, and more particularly to a subrack device which is used in a communication system based on an SDH (Synchronous Digital Hierarchy). 
     There are various specifications for communication system based on the SDH. A subrack device which is used in the communication system based on the SDH is required to have a performance in response to a particular specification of the communication system. However, to reduce the production cost, the subrack device is required to be produced flexibly to handle any one of the various specifications of the subrack device. 
     2. Description of the Prior Art 
     One example of the communication system based on the SDH will now be described. FIG. 1 shows a communication system 10 based on the SDH. In FIG. 1, a network (LINE (a high-order group)) 10A based on the SDH is shown. Also, in FIG. 1, telephone stations 11 -1  -11 -4  are shown. Subrack devices 12 of the present invention are installed in the telephone stations 11 1  -11 -4 . The telephone stations 11 -1  -11 -4  communicate through optical-fibers 13. Each of the telephone stations 11 -1  -11 -4  has a non-synchronizing hierarchy network 15 (TRIB (a low-order group)). The non-synchronizing hierarchy network 15 comprises a non-synchronizing hierarchy network device17 connected to the subrack device 12, a power-source 16 and a telephone device 18. 
     The communication system 10, as described above, has the network (LINE (a high-order group)) 11 based on the SDH and the non-synchronizing hierarchy network 15 (TRIB (a low-order group)). The communication system 10 classifies communication systems 10 -1  -10 -13  shown in FIG. 2, based on a fundamental bit rate for multiplying signals. As shown in FIG. 2, the communication system 10 -1  comprises a synchronizing network 10A having a fundamental bit rate of 155 Mbps, and a non-synchronizing network 15 having a fundamental bit rate of 2 Mbps and an impedance of 75Ω. The communication system 10 -2  comprises a synchronizing network having a fundamental bit rate of 155 Mbps, and a non-synchronizing network having a fundamental bit rate of 2 Mbps and an impedance of 120Ω. The communication system 10 -3  comprises a synchronizing network having a fundamental bit rate of 622 Mbps, and a non-synchronizing network having a fundamental bit rate of 2 Mbps and an impedance of 75Ω. The communication system 10 -4  comprises a synchronizing network in which a fundamental bit rate is 622 Mbps and a non-synchronizing network in which a fundamental bit rate is 2 Mbps and an impedance is 120Ω. The communication system 10 -7  comprises a synchronizing network in which a fundamental bit rate is 622 Mbps and a non-synchronizing network in which a fundamental bit rate is 34 Mbps and an impedance is 75Ω. 
     FIGS. 3A, 3B and 3C are schematic illustrations showing a subrack device applicable for the communication system 10 -1  shown in FIG. 2. More particularly, FIG. 3A is a perspective view showing a subrack device, FIG. 3B is a perspective view showing a back-wiring-board (BWB) assembly and FIG. 3C is a circuit diagram showing a circuit-board-unit. 
     As shown in FIG. 4A, the subrack device 20 -1  has a subrack body 21 -1  in which a plurality of circuit-board-units 22 -1  are mounted. The subrack body 21 -1  has a chassis assembly 23 -1  made of a metal plate, and a back-wiring-board (BWB) assembly 24 -1  is incorporated therein. The subrack body 21 -1  has a box-shaped circuit-board-unit housing portion 25 -1  and an outer connector arranging portion 26 -1  standing at a back face of the circuit-board-unit housing portion 25 -1 . The BWB assembly 24 -1  has a BWB 27 -1  in which connectors 28 -1 , 29 -1  for the circuit-board-units, a power-source receiving connector 30 -1  and an outer connector 31 -1  are mounted. The circuit-board-unit 22 -1  has a 75Ω impedance conversion transformer 32 -1 , as shown in FIG. 4C. The subrack device 20 -1  is used in the communication system 10 -1  and is installed in the telephone station 11 -1  in FIG. 1. The optical-fiber 13 is connected to the circuit-board-unit 22 -1  and an electrical wire 16 -1  is connected to the outer connector 31 -1  for an operation. 
     FIGS. 4A, 4B and 4C are schematic illustrations showing a subrack device applicable for the communication system 10 -2  shown in FIG. 2. More particularly, FIG. 4A is a perspective view showing a subrack device, FIG. 4B is a perspective view showing a back-wiring-board (BWB) assembly and FIG. 4C is a circuit diagram showing a circuit-board-unit. 
     As shown in FIG. 4A, the subrack device 20 -2  has a subrack body 21 -2  in which a plurality of circuit-board-units 22 -2  are mounted. The subrack body 21 -2  has a chassis assembly 23 -2  made of a metal plate and a back-wiring-board (BWB) assembly 24 -2  is incorporated therein. The subrack body 21 -2  has a box-shaped circuit-board-unit housing portion 25 -2  and an outer connector arranging portion 26 -2  standing at a back face of the circuit-board-unit housing portion 25 -2 . The BWB assembly 24 -2  has a BWB 27 -2  in which the connectors 28 -1 , 291 for the circuit-board-unit, the power-source receiving connector 30 -1  and an outer connector 31 -2  are mounted. The circuit-board-unit 22 -2  has a 120Ω impedance conversion transformer 32 -2 , as shown in FIG. 4C. The subrack device 20 -2  is used in the communication system 10 -2  and is installed in the telephone station 11 -2  in FIG. 1. The optical-fiber 13 is connected to the circuit-board-unit 22 -2  and the electrical wire 16 -2  is connected to the outer connector 31 -2  for an operation. 
     As is understood from the above description, a manufacturer has to design and produce different types of the chassis body 23 -1  (23 -2 ), the BWB assembly 24 -1  (240 -2 ) and the circuit-board-unit 22 -1  (22 -2 ) for each communication system. Therefore, the production cost of the subrack device is high. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is a general object of the present invention to provide a novel and useful subrack device by which the production cost thereof can be reduced. 
     The above object of the present invention is achieved by a subrack device comprising a subrack body comprising a chassis assembly and a back-wiring-board assembly, the subrack body having a circuit-board-unit housing portion in which a circuit-board-unit is accommodated and an outer-connecting-board mounting portion in which an outer-connecting-board is plugged, the outer-connecting-board mounting portion having a first connector and a circuit-board-unit which is accommodated in the circuit-board-unit housing portion of the subrack body, the circuit-board-unit being connected to the back-wiring-board assembly, the outer-connecting-board connected to the first connector, the outer-connecting-board being plugged in the outer-connecting-board mounting portion of the subrack body by connecting the second connector to the first connector, the outer-connecting-board being selected from outer-connecting-boards having different functions and different outer connectors in response to the different functions. 
     In the present invention, when different subrack device is produced, the same subrack body can be used. Also, since the outer-connecting-board can be plugged in the outer-connecting-board mounting portion, the outer-connecting-board can be produced separately from the subrack body. 
     According to the present invention, the subrack body, circuit-board-unit and the outer-connecting-portion can be produced and stocked separately. The subrack device required by customers can be produced by connecting the circuit-board-unit to the subrack body and plugging the selected outer-connecting-board in the outer-connecting-board mounting portion. Thus, the subrack device can be produced effectively compared with a conventional subrack device whose production process starts from building a subrack body. Also, since the same subrack body can be used commonly in all the subrack device, a number of the subrack body can be produced economically. Thus, the production cost of the subrack device can be reduced. Further, from customers&#39; side, by only replacing the outer-connecting-board to another, another subrack device can be produced economically. 
     In the above invention, the outer-connecting-board mounting portion can have a plurality of outer-connecting-board mounting territories, each of the outer-connecting-board mounting territories designed to be mounted by one of the outer-connecting-boards. In the above invention, since the outer-connecting-board mounting portion can have a plurality of the outer-connecting-board mounting territories, a plurality of outer-connecting-boards can be mounted in the outer-connecting-board mounting portion. 
     In the above invention, the outer-connecting-board can have a rectangular shape and the outer-connecting-board is arranged facing the outer-connecting-board mounting portion. Thus, the outer-connecting-board is prevented from protruding forward. Accordingly, when outer connection cables to be connected to the outer-connecting-board is provided, the area of a dead space can be reduced and the outer connection cables can be provided efficiently. 
     In the above invention, the outer-connecting-board mounting portion can be a part of the chassis assembly used for a grounding, the outer-connecting-board comprising a circuit board assembly and a rectangular shield box in which the circuit board assembly is accommodated, and a back face of the shield box contacts with the chassis assembly when the outer-connecting-board is mounted on the outer-connecting-board mounting portion. In the invention, an electromagnetic noise is prevented from leaking from the outer-connecting-board. 
     In the above invention, the outer-connecting-board mounting portion can have a positioning hole, the outer-connecting-board protruding from a back side of the outer-connecting-board mounting portion, the outer-connecting-board having a positioning pin having a tapered or spherical tip end, the positioning pin being engaged with the positioning hole when the outer-connecting-board is mounted. According to the invention, when the outer-connecting-board is plugged in the outer-connecting-portion mounting portion, the outer-connecting-portion can be positioned without using tools. 
     In the above invention, the outer-connecting-board mounting portion can have a vertical wall plate of the chassis assembly and a back-wiring-board assembly positioned in a back side of the vertical wall plate, the outer-connecting-board having a positioning pin protruding from a back side of the outer-connecting-board, the back-wiring-board assembly comprising a back-wiring-board and the first connector mounted on the back-wiring-board, the back-wiring-board having a positioning hole with which the positioning pin is engaged, the vertical wall plate having a positioning hole with which the positioning pin is engaged loosely, the positioning pin first engaging with the positioning holes of the vertical wall plate and secondly engaging with the positioning hole of the back-wiring-board when the outer-connecting-board is mounted. According to the invention, even when the outer-connecting-board is positioned roughly, the outer-connecting-board can be plugged in the outer-connecting-board mounting portion. Therefore, the connection can be conducted efficiently. 
     In the above invention, the circuit board assembly can have an impedance conversion transformer. According to the invention, regardless of the impedance of the device connected to the subrack device through an outer cables, the same circuit-board-unit can be used. Thus, the circuit-board-unit is not required to have an impedance conversion transformer and the production cost can be reduced. 
     In the above invention, the circuit board assembly can have a filtering circuit. According to the invention, a noise level leaking outside can be repressed efficiently. 
     In the above invention, the subrack body can further have a circuit board assembly having a power-source connector and a filtering circuit, and fixing/connecting means for fixing mechanically the circuit board assembly to the chassis assembly at a plurality of points and connecting electrically the filtering circuit to the chassis assembly at a plurality of points. According to the present invention, electric connecting means is not required to connect the filtering circuit to the chassis assembly. Also, since the filtering circuit is connected to the chassis assembly at a plurality of points, filtering characteristics can be improved. 
     In the above invention, the circuit-board-unit housing portion of the subrack body can have a reinforcing plate member, the reinforcing plate member having a notch at an insertion side thereof, the reinforcing plate member being provided vertically in the circuit-board-unit housing portion. In the invention, due to the notch formed in the reinforcing plate member, when the circuit-board-unit is inserted improperly, a space accepting the connector positioned at front side of the circuit-board-unit. Thus, the circuit-board-unit can be inserted from damaging the connector. That is, the circuit-board-unit is prevented from being damaged during fabrication process. Also, if the notched is not formed, a width of the reinforcing plate member must be wider. Thus, due to the notch, a mounting space for circuit-board-unit can be broadened. 
     In the above invention, the circuit-board-unit can have a unit insertion/removing tool, the circuit-board-unit housing portion of the subrack body having a receiving member with which the unit insertion/removing tool is engaged when the circuit-board-unit is mounted, and the receiving member having a cross section having a tip head shape in an insertion direction of the circuit-board-unit. In the invention, when the card lever is turned, the position of the circuit-board-unit when the card lever is engaged with the receiving member is distinct from that when the card lever is not engaged with the receiving member. Therefore, even when the circuit-board-unit is not inserted properly, the circuit-board-unit is prevented from being damaged by an operation of the card lever. 
     In the above invention, the subrack body further can have an optical-fiber handling portion which handles an excess length of the optical-fiber, the optical-fiber handling portion comprising an optical-fiber housing member in which the optical-fiber handled by the optical-fiber handling portion is accommodated and a lid member which covers the optical-fiber housing member, the optical-fiber housing member comprises a vertical wall portion and a flange portion extending inside of the optical-fiber housing member from a top of the optical-fiber housing member. According to the invention, the optical-fibers can be handled easily without a protuberance of the optical-fiber. The optical-fibers are prohibited from being placed between the lid and an optical-fiber housing portion. 
     In the above invention, the lid member can be transparent. According to the invention, the optical-fiber, particularly, how the excess length is handled, how the optical-fiber moves when the circuit board is mounted or removed, can be observed from outside. If necessary, the optical-fibers can be rehandled in order to improve a reliance of the subrack device. 
     In the above invention, the optical-fiber housing member can have a bottom-plate portion inclined upward toward a back side thereof. In this invention, the inclined bottom plate define a pass for an air current from the circuit board housing unit. Therefore, the air current in the circuit-board-unit housing portion and a heat release efficiency thereof can be improved. 
     In the above invention, the chassis body has a side plate, the side plate having a handle relatively formed by forming an opening in the side plate. According to the present invention, since another handle part is not required, the subrack device can be produced economically. Also, the optical cables can be fixed securely. 
     In the above invention, the chassis body can have a side plate, the side plate having a notch portion through which an optical-fiber is introduced into the chassis body. According to the invention, the optical-fiber can be introduced in the subrack device without bending and damaging the optical-fibers. 
     In the above invention, the back-wiring-board assembly can have only press-fit parts mounted on the back-wiring-board, the outer-connecting-board having a circuit board assembly, the circuit board assembly having only solder-jointed parts mounted on the circuit board. According to the invention, the soldering is not required in fabrication of the back-wiring-board and the press-fitting is not required in fabrication of the circuit board assembly. 
     Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic illustration showing a communication system based on a SDH; 
     FIG. 2 is a table showing a specification of the communication system shown in FIG. 1; 
     FIG. 3A is a perspective view showing a subrack device applicable for the communication system shown in FIG. 2; 
     FIG. 3B is a perspective view showing a back-wiring-board (BWB) assembly; 
     FIG. 3C is a circuit diagram showing a circuit-board-unit; 
     FIG. 4A is a perspective view showing another subrack device applicable for another communication system shown in FIG. 2; 
     FIG. 4B is a perspective view showing a back-wiring-board (BWB) assembly; 
     FIG. 4C is a circuit diagram showing a circuit-board-unit; 
     FIG. 5 is a schematic illustration showing a subrack device; 
     FIG. 6 is a circuit diagram showing an electrical connection between a BWB of the subrack device shown in FIG. 5 and an outer connecting assembly; 
     FIG. 7 is another circuit diagram showing an electrical connection between a BWB of the subrack device shown in FIG. 5 and an outer connecting assembly; 
     FIG. 8 is a perspective fabrication view showing a subrack device; 
     FIG. 9 is a schematic illustration showing an outer-connecting-board mounting portion; 
     FIG. 10 is a perspective view showing the subrack device; 
     FIG. 11 is another perspective view showing the subrack device; 
     FIG. 12 is a perspective view showing a subrack device applicable for a communication system; 
     FIG. 13 is a circuit diagram showing an electrical connection of the subrack device shown in FIG. 12; 
     FIG. 14 Is a perspective view showing a chassis assembly; 
     FIG. 15 is a perspective view showing a BWB assembly; 
     FIG. 16 is a perspective fabrication view showing an outer-connecting-board; 
     FIG. 17 is a rear and perspective view showing the outer-connecting-board shown in FIG. 16; 
     FIG. 18 is a sectional view showing the outer connecting board; 
     FIG. 19 is a perspective view showing a backside of the circuit board assembly shown in FIG. 16; 
     FIG. 20 is a schematic illustration showing a positioning of the outer-connecting-board; 
     FIG. 21 is a schematic illustration showing the outer-connecting-board; 
     FIG. 22 is a schematic illustration showing a power-source receiving portion; 
     FIG. 23 is a plan view showing a circuit board shown in FIG. 22; 
     FIG. 24 is a circuit diagram showing an power-source accepting portion; 
     FIG. 25 is a perspective view showing a blank block; 
     FIG. 26 is a schematic illustration showing an optical-fiber handling portion; 
     FIG. 27 is a perspective fabrication view showing an optical-fiber handling portion; 
     FIG. 28 is a schematic illustration showing a circuit-board-unit housing portion; 
     FIG. 29 is a schematic illustration showing the circuit-board-unit inserted improperly; 
     FIG. 30 is a schematic illustration showing a warped circuit-board-unit; 
     FIG. 31 is a schematic illustration showing a receiving member; 
     FIGS. 32A and 32B are schematic illustrations showing variations of the receiving member; and 
     FIG. 33 is a schematic illustration showing a subrack device of another embodiment of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The preferred embodiments of the present invention will now be described in further detail with reference to the accompanying drawings. 
     For a better understanding of the embodiment of the present invention, an index of the description of the preferred embodiment is listed below. 
     
         ______________________________________I      Rough Structure of the Subrack DeviceI-1    Features of the Subrack DeviceI-2    Structure of the Subrack DeviceI-3    Characteristics of the Subrack DeviceII     Embodiment of the Subrack DeviceII-1   Whole Structure of the Subrack DeviceII-2   Rough Structure of an Outer-Connection-Board  Mounting Portion of the Subrack BodyII-3   Structure of the Subrack DeviceII-4   Subrack BodyII-5   Outer Connection Board 60.sub.-1II-6   Mounting Outer Connection Board 60.sub.-1II-7   Structure and Mounting of another Outer  Connection Board 60.sub.-2, 110.sub.-1, 110.sub.-2, 111II-8   Electrical Circuit of the Outer Connection  BoardII-9   Structure of Power-Source Receiving TerritoryII-10  Blank BlockII-11  Optical-Fiber Handling PortionII-12  Structure Relating to the Optical-Fiber  Handling PortionII-13  Reinforcing Board of a Circuit-Board-Unit  Housing PortionII-14  Receiving Member of the Circuit-Board-Unit  Housing PortionIII    Subrack Device of Another Embodiment______________________________________ 
    
     I Rough Structure of the Subrack Device 
     For a better understanding of the invention, a rough structure of a subrack device of a first embodiment of the present invention will be described. In this embodiment, both a subrack device 40 -1  applicable for the communication system 10 -1  and a subrack device 40 -2  applicable for the communication system 102 are produced flexibly. The subrack device 40 -1  (40 -2 ) comprises a common structure 41 which is used for both of the communication systems 10 -1 , 10 -2  and an outer-connecting-board 60 -1  (60 -2 ) which is provided for the selected one of the communication systems 10 -1 , 10 -2 . 
     I-1 Features of the Subrack Device 
     The common structure 41 comprises a subrack body 42 and a circuit-board-unit 43. 
     The subrack body 42 comprises a chassis body 44 and a back-wiring-board (BWB) assembly 45 installed in the chassis body 44. The chassis body 44 comprises a circuit-board-unit housing portion 46 which is provided in a lower part thereof in which a circuit-board-unit 43 is accommodated and an outer-connecting-board mounting portion 47 which is provided in an upper part thereof. The BWB assembly 45 comprises a BWB 48, a circuit-board-unit connector 49 mounted in the BWB 48 and an outer-connecting-board connector 50 serving as a first connector which is also mounted in the BWB 48. The circuit-board-unit connector 49 is provided in the circuit-board-unit housing portion 46 of the chassis assembly 44. The outer-connecting-board connector 50 is provided in the outer-connecting-board mounting portion 47 of the chassis assembly 44. 
     Referring to FIG. 2, the circuit-board-unit 43 has a circuit which processes multiplied synchronizing signals in which a fundamental bit rate is 155 Mbps. In the circuit-board-unit 43, no circuit which processes non-synchronizing signals is provided. Thus, the circuit-board-unit 43 is used by both the communication system 10 -1  and the communication system 10 -2 . The circuit-board-unit 43 is inserted in the circuit-board-unit housing portion 46 and is connected to the circuit-board-unit connector 49. A front face of the circuit-board-unit housing portion 46 is sealed by a cover member (not shown). 
     Referring to FIGS. 1, 2 and 5, the outer-connecting-board connecting-board 601 corresponds to a non-synchronizing hierarchy network device171 of a fundamental bit rate 2 Mbps and an impedance of 75Ω. The outer-connecting-board 60 -1  has a structure in which a circuit board assembly 71 is accommodated in a shield box 70 made of metal. The circuit board assembly 71 comprises a circuit board 72, a second connector 73 mounted on a rear face of the circuit board 72, and an outer connector 311 mounted on a front face of the circuit board 72. The connector 73 can be connected to the above connector 50. The outer connector 31 -1  has a structure corresponding to the above non-synchronizing hierarchy network device17 -1 . The circuit board assembly 71 further has an impedance conversion transformer 32 -1  which converts an impedance to 75Ω. The connector 73 is exposed from a rear face of the shield box 70. 
     Referring to FIGS. 1, 2 and 5, the outer-connecting-board connecting-board 60 -2  corresponds to the non-synchronizing hierarchy network device17 -2  of a fundamental bit rate of 2 Mbps and an impedance of 120 Ω. The outer-connecting-board 60 -2  has a structure in which a circuit board assembly 81 is accommodated in a shield box 80 made of metal. The circuit board assembly 81 comprises a circuit board 82, a second connector 73 mounted on a rear side of the circuit board 82, and an outer connector 31 -2  mounted on a front face of the circuit board 82. The outer connector 31 -2  has a structure corresponding to the above non-synchronizing hierarchy network device17 -2 . The circuit board assembly 81 further has an impedance conversion transformer 32 -2  which converts an impedance to 120 Ω in the circuit board assembly 81. The second connector 73 is exposed from a rear face of the shield box 80, and the outer connector 31 -2  is exposed from a front face of the shield box 80. The subrack devices 40 -1 , 40 -2  comprise the above features. 
     I-2 Structure of the Subrack Device 
     In order to fabricate the subrack device 40 -1  applicable for the communication system 10 -1 , the outer-connecting-board 60 -1  is plugged in the outer-connecting-board mounting portion 47 of the common structure 41. The subrack device 40 -1  has an electrical structure shown in FIG. 6. The BWB assembly 45 is electrically connected to the circuit-board-unit 43 and to the outer-connecting-board 60 -1 . Referring to FIG. 1, the subrack device 40 -1  is installed in the telephone station 11 -1  having the non-synchronizing hierarchy network device17 -1  and is wired in the following way. First, the subrack device 40 -1  is connected to the telephone stations 11 -2 , 11 -4  , that is, optical-fibers 13 constituting the network based on the SDH are connected to the circuit-board-unit 43. Second, a connector (not shown) provided at an end of the wire 16 -1  led from the above non-synchronizing hierarchy network device17 -1  is connected to the outer connector 31 -1 . In the above structure, the subrack device 40 -1  constitutes the communication system 10 -1  to be operated. 
     In the subrack device 40 -2  applicable for the communication system 10 -2  in FIG. 2, the outer connecting board 60 -2  is plugged in the outer-connecting-board connecting-board mounting portion 47 of the common structure 41. The subrack device 40 -2  has an electrical structure shown in FIG. 7. The BWB assembly 45 is electrically connected to the circuit-board-unit 43 and to the outer-connecting-board 60 -2 . In FIG. 1, the subrack device 40 -2  is installed in the telephone station 11 -2  having the non-synchronizing hierarchy network device17 -2  and is wired in the following way. First, the subrack device 40 -2  is connected to the telephone stations 11 -1 , 11 -3 , that is, the optical-fibers 13 constituting the network based on the SDH are connected to the circuit-board-unit 43. Second, a connector (not shown) provided at an end of the wire 16 -2  led from the above device17 -2  is connected to the outer connector 31 -2 . In the above structure, the subrack device 40 -2  constitutes the communication system 10 -2  to be operated. 
     I-3 Characteristics of the Subrack Device 
     Characteristics of the subrack devices 40 -1 , 40 -2  will be described. 
     Though a manufacturer must prepare different types of outer-connecting-boards 60 -1 , 60 -2  corresponding to different types of the communication system, only one type of the common structure 41, which is a main part of the subrack, is required. Therefore, a production cost for the common structure 41 can be reduced. As a result, a production cost for the whole subrack device can be reduced compared with a conventional subrack device prepared for each type of communication device. The subrack device applicable for a desired communication system can be produced by providing the outer-connecting-board corresponding to the desired communication system 10 on the common structure 41 serving as a base. Thus, a time required for production can be shortened. 
     II Embodiment of the Subrack Device 
     II-1 Whole Structure of the Subrack Device 
     Next, the concrete structure of the subrack device roughly described above will be described in detail. 
     FIG. 8 is a perspective fabrication view showing a subrack device, which can be applicable for the communication systems 10 -1  -10 -13 . In FIG. 8, the same features as those previously described in FIG. 5 will be denoted by the same reference numerals. 
     Parts which are required for the production of the subrack device will be listed and described below. 
     (1) Subrack body 42 
     Regardless of a type of the communication system, a subrack body 42 is used commonly when the subrack device is produced. The structure thereof will be described later. 
     (2) Circuit-board-unit 43 
     A circuit-board-unit 43 is used when the subrack device applicable for the communication systems 10 -1 , 10 -2  is produced. The circuit-board-unit 43 has a circuit board 100, electrical parts 101, connectors 102, 103 and card levers 104, 105 serving as unit insertion tools. 
     (3) A Circuit-board-unit 43 -1   
     A circuit-board-unit 43 -1  is used when the subrack device applicable for the communication system 10 -3  is used. Another circuit-board-unit (not shown) used when a subrack device applicable for another communication system is used, is prepared in advance. 
     (4) Outer connecting board 60 -1   
     An outer-connecting-board 60 -1  is used when the subrack device 40 -1  applicable for the common structure 10 -1  is produced. A detailed structure thereof will be described later. 
     (5) Outer connecting board 60 -2   
     An outer-connecting-board 60 -2  is used when the subrack device 40 -2  applicable for the communication system 10 -2  is produced. A detailed structure thereof will be described later. 
     (6) Outer connecting board 110 -1   
     An outer-connecting-board 110 -1  is used when clock signal is supplied to the non-synchronizing hierarchy network device having an impedance of 75 Ω. 
     (7) Outer connecting board 110 -2   
     An outer-connecting-board 110 -2  is used when a clock signal is supplied to the non-synchronizing hierarchy network device having an impedance of 120 Ω. 
     (8) Outer connecting board 111 
     An outer-connecting-board 111 is used when the subrack device applicable for the communication system 10 -5  is produced. 
     (9) Coaxial cable 112 
     A coaxial cable 112 is used when the above outer-connecting-board 111 is used. 
     (10) Blank block 113 
     A blank block 113 is used in order to cover a blank outer-connecting-board mounting territory, when it is required. 
     II-2 Rough Structure of Outer-Connection-Board 
     Mounting Portion of the Subrack Body 
     Next, a rough structure of the outer-connecting-board mounting portion 47 of the subrack body 42 and a relationship in size between the outer-connecting-board mounting territory and the outer-connecting-board will be described. 
     The outer-connecting-board mounting portion 47 of the subrack body 42, as shown in FIG. 9, comprises outer-connecting-board mounting territories 120 -1 , 120 -2 , 120 -3 , 120 -4 , a common-connecting-portion territory 120 -5  and a power-source receiving territory 120 -6 . The outer-connecting-board mounting territories 120 -1 , 120 -2 , 120 -3  arranged horizontally in the upper portion have the same size. The rear faces of the outer-connecting-boards 60 -1 , 60 -2  and the blank block 113 have the same size as the above outer-connecting-board mounting territories. The outer-connecting-boards 110 -1  , 110 -2  have the same size as that of the outer-connecting-board mounting territory 120 -4 . The outer-connecting-board 111 has the same size as a territory which is an outer-connecting-board mounting territory 120 -3  divided by two vertically. The outer-connecting-board 60 -1  is plugged in the outer-connecting-board mounting portion 47. 
     II-3 Structure of the Subrack Device 
     Next, the structure of the subrack device applicable for each communication system will be described. 
     (1) The subrack device 40 -1  applicable for the communication system 10 -1   
     The subrack device 40 -1  comprises the subrack body 42, the circuit-board-unit 43, the outer-connecting-board 60 -1 , the outer-connecting-board 110 -1  and the blank block 113. As shown in FIG. 10, the subrack body 42 constitutes the subrack device. A plurality of circuit-board-units 43 are mounted in the circuit-board-unit housing portion 46 of the subrack body 42. The outer-connecting-board 601 is plugged in and secured by screws in the outer-connecting-board mounting territory 120 -2  of the outer-connecting-board mounting portion 47 of the subrack body 42. The outer-connecting-board connecting-board 110 -1  is plugged in and secured by screws in the outer-connecting-board mounting territory 120 -4 . In the outer-connecting-board mounting territories 120 -1 , 120 -3 , the blank block 113 is provided. The subrack device 40 -1  has the electrical connection shown in FIG. 6. 
     (2) The subrack device 40 -2  applicable for the communication system 102 
     The subrack device 40 -2  comprises the subrack body 42, the circuit-board-unit 43, the outer-connecting-board 60 -2  , the outer-connecting-board 110 -2  and the blank block 113. 
     As shown in FIG. 11, the subrack body 42 constitutes the subrack device. A plurality of circuit-board-units 43 are mounted in the circuit-board-unit housing portion 46 of the subrack body 42. The outer-connecting-board 60 -2  is plugged in and secured by screws in the outer-connecting-board mounting territory 120 -2  of the outer-connecting-board mounting portion 47 of the subrack body 42. The outer-connecting-board 110 -2  is plugged in and secured by screws in the outer-connecting-board mounting territory 120 -4 . In the outer-connecting-board-connecting-portion mounting territories 120 -1 , 120 -3 , the blank block 113 is provided. The subrack device 40 -1  has the electrical connection shown in FIG. 7. In the above two subrack devices 40 -1  , 40 -2  , the subrack body 42 and the circuit-board-unit 43 constitute the common structure 41. 
     (3) The subrack device 40 -5  applicable for the communication system 10 -5   
     The subrack device 40 -5  comprises the subrack body 42, the circuit-board-unit 43, the outer-connecting-board 111, the outer-connecting-board 110 -1  and the coaxial cable 112. 
     Since the fundamental bit rate of the non-synchronizing hierarchy network device is 34 Mbps, which is high, the coaxial cable is used instead of an electric wire in order to transmit signals at a higher bit rate. As shown in FIG. 12, the subrack body 42 constitutes the subrack device. A plurality of the circuit-board-units 43 -1  are mounted in the circuit-board-unit housing portion 46 of the subrack body 42. The outer-connecting-board 111 is plugged in and secured by screws in the lower portion of the outer-connecting-board mounting territories 120 -1 , 120 -2 , 120 -3  in the outer-connecting-board mounting portion 47 of the subrack body 42. 
     The outer-connecting-board 110 -1  is plugged in and secured by screws in the outer-connecting-board-connecting-portion mounting territory 120 -4 . One end of the U-shaped coaxial cable 112 is connected to the outer-connecting-board connecting-board 111 and the other end thereof is connected to the subrack body 42. The subrack device 40 -5  has an electrical connection shown in FIG. 13. The BWB assembly 45 is electrically connected to the circuit-board-unit 43 -1  and to the outer connecting board 111. In the BWB assembly 45, a coaxial cable 132 actually used is provided between connection terminals 130, 131. A standby coaxial cable 135 is provided between connection terminals 133, 134. The outer-connecting-board 111 has input connection terminals 136, 137 and an outer connecting terminal 138. A relay 139 is provided between input connection terminals 136, 137 and the outer connection terminal 138. When an accident occurs, the relay 139 is operated to switch the present route (coaxial cable 132 →112 -1 ) to the backup route (coaxial cable 135 →112 -2 ). 
     (4) The subrack device applicable for other communication systems. 
     This type of subrack device is also produced using a subrack body 42. 
     As is understood from the above description, when the subrack devices are produced applicable for each communication system, the subrack body 42 is used commonly. That is, the subrack body 42, which is a main part of the subrack device, is standardized. Also, each outer-connecting-board can be plugged therein. Thus, the subrack device applicable for each communication system can be produced flexibly and economically. 
     The subrack device 40 -1  is installed in, for example, the telephone station 11 -1  having the non-synchronizing hierarchy network device17 -1  shown in FIG. 1 to be operated. In this case, the optical-fibers 13 are connected to the circuit-board-unit 43. The connector (not shown) provided at the end of the electric wire 16 -1  led from the non-synchronizing hierarchy network device17 -1  is connected to the outer connector 31 -1 . 
     The subrack device 40 -2  shown in FIG. 11 is installed in, for example, a telephone station 11 -2  having the non-synchronizing hierarchy network device17 -2  to be operated. In this case, the optical-fibers 13 are connected to the circuit-board-unit 43. The connector (not shown) provided at the end of the electric wire 16 -2  led from the non-synchronizing hierarchy network device17 -2  is connected to the outer connector 31 -2 . 
     The subrack device 40 -5  shown in FIG. 12 is installed in the telephone station 11 -3  having the non-syncronizing hierarchy network device17 -3  in which the fundamental bit rate is 34 Mbps. In this case, the optical-fibers 13 are connected to the circuit-board-unit 43 -1  . The connector provided at the end of the coaxial cable 16 -3  led from the non-synchronizing hierarchy network device17 -3  is connected to the outer connector 138. 
     In the above subrack devices 40 -1  , 40 -2  , 40 -3 , the optical-fibers 13 are tied to a handle 140 formed in the chassis assembly 44 by wires 141. 
     Hereinafter, parts constituting the above subrack devices 40 -1  , 40 -2  will now be described. 
     II-4 Subrack Body 42 (Cf. FIGS. 8, 14 and 15) 
     In the subrack body 42, the BWB assembly 45 shown in FIG. 15 is provided at the rear face of the chassis body 44 shown in FIG. 14. In the subrack body 42, the circuit-board-unit housing portion 46 is provided in the lower half and the outer-connecting-board mounting portion 47 is provided in the top half, as shown in FIG. 8. 
     (1) The BWB assembly 45 
     In the BWB assembly 45, circuit board connectors 49 and outer connectors 50 are provided in the BWB 48, as shown in FIG. 15. In the bottom half 48a of the BWB 48, circuit-board-unit connectors 150, 49 are arranged in two lines. In the top half 48b of the BWB 48, connection terminals 131 -1  -131 -3  are provided in the upper part, outer connector 50 -1 , 50 -2 , 50 -3  are provided in the middle, and an outer-connecting-board connector 151 and a group of common-connecting-portion connectors 152 are provided in the lower part. All of the above connectors 49, 50 -1  -50 -3 , 150, 151, 152 and connection terminals 131 -1  -131 -3 , 134 -1  -134 -3  are press-fit parts and are secured in the BWB by press-fitting. In the BWB 48, positioning holes 153 -1  -153 -3 , 154 -1  -154 -3 , 155, 156 are formed for connectors 50 -1 , 50 -2 , 50 -3 , 151. Observing the BWB from the front, the positioning hole 153 -1  is formed diagonally up to the left of the connector 50 -1  and the positioning hole 154 -1  is formed diagonally down to the right of the connector 50 -1 . The relative position of the positioning holes 153 -2 , 154 -2  to the connector 50 -2  and the relative position of the positioning holes 153 -3 , 154 -3  to the connector 50 -3  are the same as that of the positioning holes 153 -1 , 154 -1  to the connector 50 -1 . The positioning holes 155, 156 are formed on both sides of the connector 151. In the BWB 48, an opening 157 of a rectangular shape is formed in the right side of the above common-connecting-portion connectors 152 for introducing cables. 
     (2) Chassis assembly 44 
     The chassis assembly 44, as shown in FIG. 14, has side plates 160 on both sides, the box-shaped circuit-board-unit housing portion 46 in the lower half, and a vertical wall plate 161 at the rear side of the circuit-board-unit housing portion 46. In the upper part of the circuit-board-unit housing portion 46, an optical-fiber handling portion 162 which handles an excess length of the optical-fibers is provided in the front side. 
     The vertical wall plate 161 has a plurality of openings corresponding to the upper part of the BWB assembly 45 shown in FIG. 15. In the upper part of the vertical wall plate 161, openings 163 -1 , 163 -2 , 163 -3  of a rectangular shape are formed for the connection terminals 131, 134. In the middle, openings 164 -1 , 164 -2 , 164 -3  of a rectangular shape are formed for the outer-connecting-board connector 50. The relative position of positioning holes 165 -1  -165 -3 , 166 -1  -166 -3  to the openings 164 -1  -164 -3  is the same as that of the positioning holes 153 -1  -153 -3 , 154 -1  -154 -3  to each of the connectors 50 -1  -50 -3 . In the lower portion, a rectangular opening 167 for the outer-connecting-board connector and openings 168, 169 for the common-connecting board connectors 152 are formed. The relative position of the two positioning holes 170, 171 to the opening 167 is the same as that of the positioning holes 155, 156 to the connector 151 of the BWB assembly 45. In the vertical wall plate 161, a plurality of screw holes 172 are formed. When the BWB assembly 45 is fixed to the rear side of the chassis assembly 44, the circuit-board-unit housing portion 46 and outer-connecting-board mounting portion 47 are formed in a way to be described later. 
     (a) The circuit-board-unit housing portion 46 
     A lower-half portion 45a of the BWB assembly 45 covers the rear side of the circuit-board-unit housing portion 46. The connectors 150, 49 are arranged in the circuit-board-unit housing portion 46. 
     (b) The outer-connecting-board mounting portion 47 
     An upper-half portion 45b of the BWB assembly 45 faces the rear face of the vertical wall plate 161. 
     As shown in FIG. 8, the connecting terminals 131 -1 , 134 -1 , 131 -2  , 134 -2 , 131 -3 , 134 -3  are exposed from the openings 163 -1 , 163 -2 , 1633. The connectors 50 -1 , 50 -2 , 50 -3  protrude from the openings 164 -1 , 164 -2 , 164 -3  respectively. The positioning holes 165 -1  -165 -3 , 166 -1  -166 -3  face the positioning holes 153 -1  -153 -3 , 154 -1  -154 -3  (Cf. FIG. 20). The connector 151 protrudes from the opening 167. The positioning holes 170, 171 face the positioning holes 155, 156. The common-connecting-portion connectors 152 are exposed from the opening 168. The connecting terminals 131 -1 , 134 -1 , the connector 50 -1  and the positioning holes 165 -1 , 166 -1  are provided in the outer-connecting-board mounting territory 120 -1  shown in FIG. 9. The connecting terminals 131 -2  , 134 -2 , the connector 50 -2  and the positioning holes 165 -2 , 166 -2  are provided in the outer-connecting-board mounting territory 120 -2  shown in FIG. 9. The connecting terminals 131 -3 , 134 -3 , the connector 50 -3  and the positioning holes 165 -3 , 166 -3  are provided in the outer-connecting-portion mounting territory 120 -3  shown in FIG. 9. The outer-connecting-board connector 151 and the positioning holes 170, 171 are formed in the outer-connecting-board mounting territory 120 -4  shown in FIG. 9. The common-connecting-portion connectors 152 are provided in the outer-connecting-board mounting territory 120 -5  shown in FIG. 9. 
     II-5 Outer Connection Board 60 -1  (FIGS. 8, 16, 17, 18 and 19) 
     In the outer-connecting-board 60 -1 , the circuit board assembly 71 is provided in the shield box 182 of a rectangular shape in which a box body 180 and a lid 181, which are made of metal, are combined. 
     The circuit board assembly 71 comprises the circuit board 72, a plurality of the outer connectors 31 -1 , the impedance conversion transformer 32 -1  of 75Ω, the connector 73 and two positioning pins 183, 184, as shown in FIGS. 16 and 19. The outer connector 31 -1  is arranged in the surface of the circuit board 72 in a matrix formation. The impedance conversion transformer 31 -1  is provided in the rear surface of the circuit board 72 corresponding to each outer connector 31 -1 . The connectors 73 are mounted in the lower part of the rear surface of the circuit board 72. The above outer connector 31 -1 , the impedance conversion transformer 32 -1  and the connectors 73 are mounted in the circuit board 72 by soldering. The positioning pins 183, 184 have a cylindrical shape and are secured in the circuit board 72 by screws. The positioning pins 183, 184 protrude to the rear face of the circuit board 72. The relative position of the positioning pins 183, 184 to the connector 73 is the same as that of the positioning holes 153 -1 , 154 -1  to the connector 50 -1  shown in FIG. 15. The tip end of the positioning pins 183, 184 is tapered or spherical to be inserted easily. The box body 180 has a flat bottom plate 180a and a side-plate portion 180b of a square-frame shape. In the bottom plate portion 180a, an opening 180a -1  for the connector 73 and openings 180a -2 , 180a 31  3 for the positioning pins 183, 184 are formed. In the side-plate portion 180b, a seat portion 180b -1  on which the circuit board assembly 71 is secured is formed. A lid 181 has a lid-plate portion 181a and a side-plate portion 18lb of a square frame shape. The lid-plate portion 181a has a plurality of holes 181a -1  formed in the same formation as that of the outer connectors 31 -1 . 
     The circuit board assembly 71 is, as shown in FIG. 18, fixed in the box body 180 by the circuit board 72 being secured in the seat portion 180b -1 . The circuit board assembly 71 is accommodated in the box body 180. As shown in FIG. 17, the connectors 73 are exposed from the opening 180a -1 . The positioning pins 183, 184 protrude from the rear face of the outer-connecting-board 61 -1  through the openings 180a -2 , 180a -3 . 
     A side-plate portion 18lb of the lid 181 is engaged with outside of the side-plate portion 180b of the box body. Between the side-plate portions 181b along four sides, electromagnetic noise shield gaskets 185 which have a plurality of springs 185 are provided. That is, the outer-connecting-board 60 -1  has an anti-electromagnetic noise mechanism. The outer-connecting-board 60 -1  has four screws 186 -1  -186 -4  and a handle 187. The screws 186 -1  -186 -4  have a bar shape which has thread portions 186 -1a  -186 -4a  at one end and nob portions 186 -1b  -186 -4b  at the other end. The screws 186 -1  -186 -4  protrude from the box 182 at a left-upper point and a left-lower point. The thread portions 186 -la  -186 -4a  protrude from the rear face of the box 182 and the nob portions 186 -1b  -186 -4b  protrude from the front face of the box 182. 
     II-6 Mounting Outer Connection Board 60 -1   
     The outer-connecting-board 60 -1  is provided in a desired mounting territory by the following steps. 
     (1) Place the outer-connecting-board 60 -1  in the desired outer-connecting-portion mounting territory 120 -2 . 
     (2) The positioning pins 183, 184 and the positioning holes 165 -2 , 166 -2  are mated. The outer-connecting-board 60-1 is urged to the outer connecting mounting portion 47. 
     (3) The screws 186 -1  -186 -4  are tightened. 
     As shown in FIG. 20, a diameter d 1  of the positioning pin 184, a diameter d 2  of the positioning hole 166 -2  formed in the vertical wall plate 161 of the chassis assembly 44 and a diameter d 3  of the positioning hole 154 -2  formed in the BWB 48 have the following relationship. 
     
         d.sub.1 &lt;d.sub.3 &lt;d.sub.-2 
    
     Thus, the positioning pin 184 is inserted easily into the hole 166 -2  in the first step and is engaged with the hole 154 -2  in the second step. The other positioning pin 183 is inserted easily into the hole 165 -2  and is engaged with the hole 153 -2 . Thus, the outer-connecting-board 60 -1  is roughly positioned in the above first step and accurately positioned in the second step to connect the connector 73 to the connector 50 -2  smoothly and properly. 
     When the screws are tightened securely, a whole surface of the bottom portion 180a contacts the vertical wall plate 161, as shown in FIG. 21. Thus, the outer-connecting-board 60 -1  contacts the chassis assembly over a large area and is grounded securely. As described above, since the outer-connecting-board 60 -1  has a shield box structure and is grounded by connecting to the chassis assembly 44, a radiation of the electromagnetic noise from the outer-connecting-board 60 -1  is repressed when operated. The above outer-connecting-boards 60 -1  are mounted in the other connecting portion mounting territories 120 -1 , 120 -2 . 
     When the outer-connecting-board 60 -1  is mounted in the mounting territory, the circuit board assembly 71 (circuit board 72) is parallel to the BWB 48 (BWB assembly 45). That is, the outer-connecting-board 61 -1  faces the outer-connecting-board mounting portion 47. Thus, territories in which an outer cable connected to the outer connector 31 -1  is provided can be formed efficiently. That is, when the outer-connecting-board 60 -1  is provided vertically in the mounting portion 47, a dead space in which the outer cable cannot be provided is formed. 
     II-7 Structure and Mounting of other Outer 
     Connection Boards 60 -2 , 110 -1 , 110 -2 , 111 
     The outer-connecting-boards 60 -2  have the same structure as the above outer-connecting-board 60 -1  except the outer connector 31 -2  and an impedance conversion transformer of 120Ω (not shown), as shown in FIG. 11. 
     The outer-connecting-board 60 -2  is fixed in the outer-connecting-portion mounting territories 120 -1 , 120 -2 , 120 -3  as well as the above outer-connecting-board 60 -1 . As shown in FIG. 8, outer-connecting-boards 100 -1 , 100 -2  have substantially the same structure as the above outer-connecting-board 60 -1 . As shown in FIGS. 9, 10 and 11, the outer-connecting-boards 100 -1 , 100 -2  are secured in the outer-connecting-portion mounting territory 120 -4  in the following way. The positioning pins 190, 191 are inserted into the positioning holes 170, 155, and 171, 156. After that, the positioning pins 190, 191 are connected to the connector 151 and are secured by screws. As shown in FIG. 8, the outer-connecting-board 111 has a size half of the above outer-connecting-board 60 -1  and has substantially the same structure as the outer-connecting-board 60 -1 . The outer-connecting-board 111 is, as shown in FIG. 12, positioned by the positioning pins and positioning holes. The outer-connecting-board 111 is connected and secured to the connector 50 -1  by screws to be fixed in the lower-half portion of the outer-connecting-portion mounting territories 120 -1 , 120 -2 , 120 -3 . 
     II-8 Electrical Circuit of Outer Connection 
     Boards 60 -1 , 60 -2   
     (1) The outer-connecting-board 60 -1  (FIGS. 6, 16 and 19) 
     The circuit board assembly 71 shown in FIGS. 16 and 19 has a 75Ω impedance conversion transformer 32 -1  and a filtering circuit 195. 
     Mismatch loss characteristics are prevented from being deteriorated by the 75Ω impedance conversion transformer 32 -1 . Also, only one wiring is required between the outer-connecting-board 60 -1  and BWB assembly 45 per one channel. 
     The filtering circuit 195 is provided between the impedance conversion transformer 321 and the outer connector 31 -1  . In the filtering circuit 195, coils L 1 , L 2  and a capacitor C 1  are connected in a way as shown in FIG. 6. Since the filtering circuit 195 is provided, a noise level, which is generated in the subrack, is transmitted through the outer-connecting-board 61 -1  and a leak from the outer connector 31 -1  to the outside of the subrack device 40 -1  can be reduced effectively. 
     (2) The outer-connecting-board 60 -2  (FIG. 7) 
     The outer-connecting-board 60 -2  has, as shown in FIG. 7, a 120Ω impedance conversion transformer 32 -2  and a filtering circuit 196. 
     The filtering circuit 196 comprises coils L 3 , L -4  and a capacitor C -2 . 
     The impedance conversion transformer 32 -2  functions in the same way as the impedance conversion transformer 32 -1  of the outer-connecting-board 60 -1  . The filtering circuit 196 functions in the same way as the filtering circuit 195 of the outer-connecting-board 60 -1  . 
     II-9 Structure of Power Source Receiving Territory 
     120 -6   
     As shown in FIG. 22, a power-source receiving portion 200 has a circuit board assembly 201, which is separated from the BWB 48. 
     The circuit board assembly 201 comprises a circuit board 202 shown in FIG. 23, power-source connectors 203, 204 mounted thereon, capacitor chips 205 -1  -205 -5  mounted thereon, load terminals 206 -1  -206 -3  and grounding terminals 207 -1  -207 -4  serving as securing/connecting means. 
     The circuit board 202 has a wiring pattern 208 shown in FIG. 23. The capacitor chips 205 -1  -205 -5  mounted in the circuit board 202 are shown as a tow-dotted chain line in FIG. 23. The capacitor chips 205 -1  -205 -5  are electrically connected in a way as shown in FIG. 24 to constitute a filtering circuit 209. The filtering circuit 209 functions to reduce a noise level which leaks from the subrack device 40 -1  through the power-source receiving portion 200 to the power-source cable. 
     The wiring pattern 208 has a frame pattern portion 208a along a periphery of the circuit board 202. At each corner of the frame pattern portion 208a, grounding terminals 207 -1  -207 -4  are secured by soldering. Each grounding terminal 207 -1  (207 -2  -207 -4 ) is a metal part of a bent shape which has a screw hole 207 -1a  and foot portions 207 -1b . Each grounding terminal 207 -1  (207 -2  -207 -4 ) is secured at each corner of the circuit board 202 by the foot portions 207-1b being solder-joined and thus being electrically connected to the wiring pattern 208. The grounding terminals 207 -1  -207 -4  of the circuit board assembly 201 are secured at positions adjacent to the openings 169 of the vertical wall plate 161 by screws 211. One end of the electrical wire 212 is connected to the load terminals 206 -1  (206 -2 , 206 -3 ). The electrical wire 212 is introduced through the opening 157 and is connected to the terminals 213 on the BWB 48. The circuit board assembly 201 is covered with a cover member 214 made of metal with the power-source connector 203, 204 being exposed. The power-source connectors 203, 204 are connected to connectors 217, 218 of the power-source cable 215, 216 in the telephone station. 
     Next, a connecting portion between the above filtering circuit 209 and the frame ground will be described. The filtering circuit 209 is connected to the frame ground at a plurality of, for example four, positions. Thus, the filtering circuit 209 can reduce the leaking noise level effectively compared with that connected at one position. Therefore, a noise level leaking from the subrack device 40 -1  to the power-source cable 215, 216 through the power-source receiving portion 200 can be reduced according to the present embodiment. The electrical connections between the filtering circuit 209 and the frame ground at four points are made by the grounding terminal members 207 -1  -207 -4  which secure mechanically the circuit board assembly 201 to the vertical wall plate 161 and screws 211. That is, mechanical fixing means function as electrical connecting means. Therefore, the number of parts can be reduced compared with a subrack device in which mechanical securing means and electrical connecting means are provided separately. As shown in FIG. 22, the subrack device 40 -1  has a rear cover 219 which covers the rear side of the BWB assembly 45. 
     II-10 Blank Block (FIGS. 25, 9, 10 and 11) 
     The blank block 113 comprises a blank block body 130 and four screws 186 -1  -186 -4  which pass through the blank block body 130, as shown in FIG. 25. 
     The blank block body 130 is formed by bending a metal plate, which comprises a box portion 130a and flange portions 130b, 130c which extend upward and downward. The blank block body 130 has the same size as the outer-connecting-board 60 -1  (60 -2 ). 
     The blank block 113 is mounted using screws in the outer-connecting-portion mounting territories 120 -1 , 120 -3  in which the outer-connecting-board 60 -1  (60 -2  ) is not mounted, as shown in FIGS. 10 and 11. 
     II-11 Optical-Fiber Handling Portion (FIGS. 8, 26, 27) 
     As shown in FIG. 8, the subrack body 21 -1  has an optical-fiber handling portion 210 on a front side of the circuit-board-unit housing portion 46. 
     The optical-fiber handling portion 210 has an optical-fiber housing member 211 and a lid member 212 made of transparent resin. As shown in FIGS. 26 and 27, the optical-fiber housing member 211 having a rectangular shape has a bottom plate 211a, a vertical wall 211b on a front side, and a vertical wall 211c on a back side. The optical-fiber housing member 211 has a width A. The width A is 60 mm, which is twice as much as an allowable minimum bending radius of the optical-fiber. The bottom-plate portion 211a has a plate portion 211a -1  on a front side and an inclined portion 211a -2  on a back side which is inclined upward to backward. The inclined portion 211a -2  is provided in order to improve a heat release efficiency. The vertical wall 211b on the front side has a plurality of notches 211b -1 . The notches 211b -1  reach the bottom-plate portion 211a. The notches 211b -1  function as passes for optical-fibers which extend downward. The vertical wall 211b on the front side has tooth portions 211b -2  between adjacent notches 211b -1 . The vertical standing wall 211c on the back side comprises a vertical wall 211c -1  and a flange portion 211c -2  which is extending inside from the top of the vertical wall 211c. The flange portion 211c -2  prevents an excess length of the optical-fiber from protuberating. The width B is 5 mm. The optical-fiber housing member 211 has lid fixing portions 211d at both sides along the length. 
     The optical-fiber housing member 211 has a U shape observed along the width length. Both ends of the optical-fiber housing member 211 are formed in openings 211e. The optical-fiber 13 -1  is introduced in the optical-fiber housing member 211. The optical-fiber 13 -1  is handled by being wound counterclockwise in a space defined by the standing wall portions 211b, 211c and the front-side standing wall 211b. After that, the optical-fiber 13 -1  is introduced to the circuit-board-unit housing portion 46 through the notch 211b -1 . The tip end of the optical-fiber 13 -1  is connected to a connector 216 of an optical-electric conversion portion of the circuit-board-unit 43, as shown in FIG. 22. 
     A reference numeral 215 -1  indicates the excess length of the optical-fiber. The excess length of the other optical-fibers 13 -2 , 13 -3  are handled in the same way as that of the above optical-fiber 13 -1 . The optical-fibers 13 -2 , 13 -3  are introduced to the circuit-board-unit housing portion 46 through the notch 211b -1 . The excess length of the optical-fiber 215 -1  -215 -3  are partly overlapped, as shown in FIG. 27. In the excess length of the optical-fibers 215 -1  -215 -3  handled by the inclined portion 211a -2 , the optical-fibers adjacent to the inside standing wall portion 211c are, as shown in FIG. 26, inclined upward. In the excess length of the optical-fibers 215 -1  -215 -3  handled by the inclined portion 211a -2 , especially the optical-fibers adjacent to the inside standing wall portion 211c tend to be protuberant. When the lid member 212 is fixed in such case, the protuberant portion of the optical-fibers is placed between the lid portion and the standing wall portion 211b on the front side, which may lead to damage to the optical-fibers. 
     On the contrary, since the flange portion 211c -2  is provided in this embodiment, protuberant portions of the excess length of the optical-fibers 215 -1  215 -3  are held down by the under-surface of the flange portion 211c -2 . Thus, when the lid portion is fixed on the optical-fiber housing portion 211, the optical-fibers are not placed between them and the optical-fiber is not damaged. The lid member 212 is fixed on the optical-fiber housing member 211 covering the excess length of the optical-fibers 215 -1  -215 -3  by fixing tools 213, as shown in FIG. 26. Since the lid member 212 is transparent, the optical-fiber in the optical-fiber housing unit 211, particularly, how the excess length is handled, how the optical-fiber moves when the circuit board is mounted or removed, can be observed from outside. In FIG. 27, at the top of the vertical standing wall 211b (tooth portion 211b -2 ), a flange of a bent shape can be provided. 
     II-12 Structure Relating to the Optical-Fiber 
     Handling Portion 
     A handle 140 for tying the optical-fibers 131 -1  -13 -3  is formed by forming an opening 220 by pressing a part of the side plate 160 of the chassis assembly 44, as shown in FIGS. 26 and 27. The side plate 140 has a U-shaped notch 221, as shown in FIG. 25. The U-shaped notch 221 functions as an introducing hole of the subrack device for the optical-fibers 13 -1  -13 -3 , as shown in FIG. 27. 
     An inclined portion 211a -2  of the bottom plate portion 211a of the optical-fiber housing member 211 defines a pass 223 for air current 222 rising from the circuit-board-unit housing portion 46, as shown in FIG. 26. By the features described above, the air current 222 flows smoothly compared with a subrack device having only a flat bottom-plate portion 211a but not having the inclined portion 211a -2 . Thus, in the circuit-board-unit housing portion 46, smooth air currents are available and a heat generated in the circuit-board-unit 43 can be released efficiently. 
     II-13 Reinforcement Board of a Circuit-Board-Unit 
     Housing Portion (FIGS. 8, 22, 28, 29, 30) 
     As shown in FIGS. 14 and 28, the circuit-board-unit housing portion 46 has side boards 160 provided on both right and left sides, a bottom plate 230, a top plate 231, receiving members 232, 233 and a reinforcing plate 234. 
     In the bottom plate 230 and the top plate 231, the guide rail 231 is provided. The reinforcing plate 234 is provided between the side plates 160 on both the right side and the left side in the same direction of the circuit-board-unit, which is parallel to the housed circuit-board-unit. The reinforcing plate 234 is secured to the bottom plate 230 and top plate 231 by screws to reinforce the circuit-board-unit housing portion 46 of the box shape. The receiving members 232, 233 are respectively secured on a front side of the bottom plate 230 and the top plate 231. In the bottom plate 230 and the top plate 231, the guide rails 230a, 231a are provided to guide the bottom and top portions of the circuit board 100 of the circuit-board-unit 43. 
     The reinforcing plate 234 has notches 234a of a rectangular shape in one edge adjacent to a circuit-board-unit insertion opening of the circuit-board-unit housing portion 46. The notch 234a has a size in which the connectors 102, 103 of the circuit-board-unit 43 can be included just after the circuit board unit 43 is inserted. 
     The size of the notch 234a is determined based on the circuit-board-unit 43 in the following way. 
     Lower edge 234a -1  : Little bit lower than the lower edge of the connector 102 
     Upper edge 234a -2  : Little bit higher than the top edge of the connector 102 
     Internal edge 234a -3  : a -1  &gt;a -2   
     In the above, a -1  indicates a distance from the beginning end of the guide rail 230a (231a) to the edge 234a -3  and a -2  indicates a length of the connectors 102, 103 which protrudes from the circuit board. 
     Next, advantages of the above notch 234a will be described. The notch 234a prevents the connectors 102, 103 from colliding with the reinforcing plate 234 when the circuit-board-unit 43 is inserted into the guide rail 230a, 231a in a wrong way, as shown in FIGS. 29, 30. 
     FIG. 29 shows the circuit-board-unit 43 inserted in a left direction, which is different from a proper direction. The connector 103 (102) is accepted in the notch 234a and does not collide against the reinforcing plate 234. When the circuit-board-unit 43 is inserted deeply and the circuit board 100 is guided by the guide rails 230a, 231a, the circuit-board-unit 43 is corrected in position as shown by two-dotted-chain line in FIG. 29, which is a normal position of the circuit-board-unit 43. Thus, the circuit-board-unit 43 is inserted without the connectors 102, 103 colliding against the reinforcing plate 234. 
     FIG. 30 shows the circuit-board-unit 43 warped when it is inserted. In this case also, the connectors 102, 103 are accepted in the notch 234a and do not collide against the reinforcing plate 234. When the circuit-board-unit is inserted deeply and the circuit board 100 is guided by guide rails 230a, 231a, the warped circuit-board-unit 43 is corrected to a normal shape as shown by a two-dotted-chain line. Thus, the circuit-board-unit 43 is inserted without the connectors 102, 103 colliding against the reinforcing plate 234. 
     II-14 Receiving Member of the Circuit-Board-Unit 
     Housing Portion (FIGS. 8, 31, 32) 
     The receiving member 232 has an upper surface 240, as shown in FIG. 31. In FIG. 31, X1 represents an insertion direction of the circuit-board-unit 43 and X2 represents a pulling-out direction thereof. 
     The upper surface 240 comprises a tip head portion 240a provided in an end towards the X 1  direction and an inclined face inclining downward towards the X2 direction. The tip head portion 240a has a round portion whose radius R is 0.1 mm. When the circuit-board-unit 43 is inserted and the card lever 104 is turned clockwise, the stopper portion of the card lever 104 is engaged with an inner surface 241 of the receiving member 232 and the circuit-board-unit 43 is connected to the BWB assembly 45 properly. 
     When the circuit-board-unit 43 is inserted in an improper slot and the card lever 104 is turned clockwise, the stopper nail portion 104a slides on the inclined surface portion 240b. Thus, the receiving member 232 is not urged downward and the circuit-board-unit housing portion 46 is not damaged. Also, a strong force is not applied to the circuit-board-unit 43 and the circuit board 100 and the card lever 104 are not damaged. The upper-side receiving member 232 has a symmetrical shape to the receiving member 232 and the functions the same as the receiving member 232. The above structure is especially effective when a unit-insertion-error insertion-error preventing portion has a small size in a front-back direction and a distance between the position of the circuit-board-unit at which the circuit-board-unit contacts the unit-insertion-error preventing portion and a position of a pin when the circuit-board-unit contacts the unit-insertion-error preventing portion. 
     FIGS. 32A and 32B show variations of the receiving member. 
     A receiving member 232A shown in FIG. 32A has an upper surface 240A. The upper surface 240A comprises a tip head portion 240Aa provided at an end towards the X2 direction and an inclined surface 240Ab inclined downward toward the X1 direction. A receiving member 232B shown in FIG. 32B has an upper surface 240B. The upper surface 240B comprises a tip head portion 240Ba provided in the middle and inclined surfaces 240Bb, 240Bc provided at both sides of the tip head portion 240Ba. The above receiving members 232A, 232B function approximately the same as the receiving member 232. 
     III Subrack Device of Another Embodiment 
     FIG. 33 shows subrack devices 40A -1 , 40A -2  of another embodiment. In the subrack devices 40A 1 , 40A -2 , the outer-connecting-boards 60 -1 , 60 -2  are respectively plugged in the rear side of the circuit-board-unit housing portion 46 in the common structure 41A. 
     Further, the present invention is not limited to these embodiments, but various variations and modifications may be made without departing from the scope of the present invention.