Abstract:
A transmission apparatus includes: a generator configured to generate position information indicating a position of header information of each of a plurality of first signals from a second signal nesting the plurality of first signals; a storage configured to store the position information generated by the generator and the plurality of first signals; a monitor configured to read the position information and the plurality of first signals stored in the storage, and to monitor the header information of each of the plurality of first signals based on the position information; and an output unit configured to output the plurality of first signals after monitoring the contents of the header information.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2015-099322, filed on May 14, 2015, the entire contents of which are incorporated herein by reference. 
     FIELD 
     The embodiments discussed herein are related to a transmission apparatus and a transmission method. 
     BACKGROUND 
     An optical transport network (OTN) transmission method specified in the International Telecommunication Union (TIU)-TG.709 standard is a method of transmitting client signals flowing into the optical network while storing the client signals in an optical channel transport unit (OTU). In addition to the payload storing the client signals, the OTU stores an overhead (OH) of an optical channel payload unit (OPU), an OH of an optical channel data unit (ODU), and an OH of the OTU. 
     In the OTN, a plurality of types of OTUs are defined capable of storing a plurality of types of client signals having different transmission rates as one signal. For example, client signals of up to about 1.25 Gbps are stored in an OTU0, and client signals of up to about 2.5 Gbps are stored in an OTU1. In addition, client signals of up to about 10 Gbps are stored in an OTU2, client signals of up to about 40 Gbps are stored in an OTU3, and client signals of up to about 100 Gbps are stored in an OTU4. Further, multiple types of ODUs are stored in the OTU. 
     As for the multiple types of ODUs, for example, client signals of up to about 1.25 Gbps are stored in an ODU0, and client signals of up to about 2.5 Gbps are stored in an ODU1. In addition, client signals of up to about 10 Gbps are stored in an ODU2, client signals of up to about 40 Gbps are stored in an ODU3, and client signals of up to about 100 Gbps are stored in an ODU4. 
     Lower-level ODUs are stored in the ODU. For example, the ODU0, ODU1, ODU2, and ODU3 are stored in the ODU4, and the ODU0, ODU1, and ODU2 are stored in the ODU3. Moreover, the ODU employs a multi-stage method capable of storing the lower-level ODUs to be nested in multiple stages. Further, the ODU which stores the lower-level ODUs is a higher order (HO)-ODU. The ODU which does not store the lower-level ODUs is a lower order (LO)-ODU. The ODU4 is obtained by, for example, multiplexing two HO-ODU2s, each storing eight LO-ODU0s, and two HO-ODU3s, each storing four LO-ODU2s. 
     Further, a separation unit of the transmission apparatus that conforms to the OTN separates the HO-ODU in a payload area of the received OTU and separates the data of the LO-ODU from the separated HO-ODU. Further, a multiplexing unit of the transmission apparatus stores the data of the LO-ODU in the HO-ODU, and outputs the stored HO-ODU while storing in the payload area of the OTU. 
       FIG. 14  is an explanatory diagram illustrating an example of a transmission system  100 . The transmission system  100  illustrated in  FIG. 14  includes client devices  101  of the OTU1, a network  102  of the OTU2, and a transmission apparatus  103 . The transmission apparatus  103  is, for example, a transmission apparatus corresponding to OTU1×4 and OTU2×1. 
     The transmission apparatus  103  includes an OTU1 I/F  111 , an ODU1 MUX/DMUX (Multiplexer/Demultiplexer)  112 , a XC (Cross Connect)  113 , an ODU processing unit  114 , an ODU2 MUX/DMUX  115 , and an OTU2 I/F  116 . The OTU1 I/F  111  is a communication I/F between the transmission apparatus  103  and the client devices  101  of the OTU1. The OTU1 I/F  111  executes a calculation processing such as forward error correction (FEC) of the OTU1, and performs an error correction from the calculation results. 
     Further, the OTU1 I/F  111  detects the synchronization of an OTU OH of the OTU1. Further, the detection of the synchronization of the OH is performed by identification using a frame alignment signal (FAS) of the OTU OH of the OTU1. The OTU1 I/F  111  has an OH processing unit  111 A which monitors the contents of the OTU OH while inserting the contents of the OTU OH into the OH area of the OTU1. The OH processing unit  111 A has a register for each OTU1 I/F  111  to shift OTU1s to each other in order to ensure the synchronization between OTU1s of the OTU1 I/F  111 . The number of OH processing units  111 A is four in order to correspond to the OTU1 I/Fs  111 . 
     The ODU1 MUX/DMUX  112  has a de-multiplex (DMUX) function of separating the data of the ODU0 which is the LO-ODU from the ODU1 which is the HO-ODU in the OTU1, and a multiplex (MUX) function of storing the data of the ODU0 in the ODU1. The XC  113  rearranges and outputs each data to a predetermined output destination on a LO-ODU basis. The ODU processing unit  114  has an OH processing unit  114 A to monitor the contents of the ODU OH while inserting the ODU OH into an OH area of the ODU. The OH processing unit  114 A has a register to shift data of the LO-ODUs to each other in order to ensure the synchronization between the data of the LO-ODUs on a LO-ODU basis. The number of the OH processing units  114 A is eight in a total for each LO-ODU. 
     The ODU2 MUX/DMUX  115  has a DMUX function of separating the data of the ODU0 which is the LO-ODU from the ODU2 which is the HO-ODU, and a MUX function of storing the data of the ODU0 in the ODU2. 
     The OTU2 I/F  116  is a communication I/F between the transmission apparatus  103  and the network  102  of the OTU2. The OTU2 I/F  116  performs the FEC calculation processing of the OTU2, and inserts an FEC value into an FEC area of the OTU2. Further, the OTU2 I/F  116  detects the synchronization of an OTU OH of the OTU2. Further, the detection of the synchronization of the OTU OH is performed by identification using the FAS of the OTU OH of the OTU2. The OTU2 I/F  116  has an OH processing unit  116 A which monitors the contents of the OTU OH while inserting the contents of the OTU OH into the OH area of the OTU2. 
     The OH processing unit  111 A of the OTU1 I/F  111 , upon receiving the OTU1 from the client device  101 , checks the contents of the OTU OH of the OTU1, and then outputs the OTU1 to the ODU1 MUX/DMUX  112 . 
     The ODU1 MUX/DMUX  112  separates the data of the ODU0 from the ODU1 in the OTU1, and outputs the separated data of the ODU0 to the XC  113 . The XC  113  rearranges the data of the ODU0 from the ODU1 MUX/DMUX  112  to a predetermined output destination on a LO-ODU basis. Each OH processing unit  114 A of the ODU processing unit  114  monitors the contents of the ODU OH of each ODU0. Further, each OH processing unit  114 A, upon detecting a rewrite request of the ODU OH of each ODU0, rewrites a part or all of the contents of the ODU OH of each ODU0. 
     After the OH processing of the ODU OH of the ODU0, each OH processing unit  114 A outputs the data of the ODU0 completed with the OH processing to the ODU2 MUX/DMUX  115 . The ODU2 MUX/DMUX  115  stores the data of the ODU0 completed with the OH processing in the ODU2, stores the ODU2 in the payload area of the OTU2, and outputs the OTU2 to the OTU2 I/F  116 . 
     The OH processing unit  116 A of the OTU2 I/F  116  inserts the contents of the OTU OH into the OH area of the OTU2. Then, the OTU2 I/F  116  inserts the FEC value from the FEC calculation processing into the FEC area of the OTU2, and outputs the OTU2 to the network  102 . 
     When transmitting the OTU1 of each client device  101  to the network  102  as the OTU2, the transmission apparatus  103  monitors the contents of the OTU OH of the OTU1, and then monitors and inserts the contents of the ODU OH for each LO-ODU in the OTU1. As a result, the transmission apparatus  103  stores the LO-ODU0 of each OTU1 from each client device  101  in the OTU2, and output the OTU2 to the network  102 . 
     Upon receiving the OTU2 from the network  102  of the OTU2, the OTU2 I/F  116  identifies the FAS in the OTU OH of the OTU2 and detects the synchronization of the OTU2. Further, the OH processing unit  116 A of the OTU2 I/F  116  monitors the contents of the OTU OH of the OTU2. The OTU2 I/F  116  separates the ODU2 from the payload area in the OTU2 and outputs the ODU2 to the ODU2 MUX/DMUX  115 . The ODU2 MUX/DMUX  115  separates the data of the ODU0 from the ODU2 in the OTU2, and outputs the separated data of the ODU0 to the ODU processing unit  114 . 
     Each OH processing unit  114 A of the ODU processing unit  114  monitors the contents of the ODU OH of the ODU0 from the ODU2 MUX/DMUX  115  and, when rewriting the contents of the ODU OH, rewrites the contents of the ODU OH. The ODU processing unit  114  outputs the data of the OUD0 completed with the OH processing to the XC  113 . 
     The XC  113  rearranges the data of each ODU0 from the ODU processing unit  114  to a predetermined output destination on a LO-ODU basis, and outputs the data of each ODU0 to the ODU1 MUX/DMUX  112 . The ODU1 MUX/DMUX  112  stores the ODU0 from the XC  113  in the ODU1, stores the ODU1 in the payload area of the OTU1, and outputs the OTU1 to the OTU1 I/F  111 . The OTU1 I/F  111  stores the ODU1 from the ODU1 MUX/DMUX  112  in the payload area of the OTU1, and inserts the contents of the OTU OH into the OH area of the OTU1. Further, the OTU1 I/F  111  FEC calculates the OTU1, and inserts the FEC value into the FEC area in the OTU1. Then, the OTU1 I/F  111  outputs the OTU1 to the client device  101 . 
     When transmitting the OTU2 from the network  102  to each client device  101 , the transmission apparatus  103  monitors the OTU OH of the OTU2, and then monitors and inserts the contents of the ODU OH for each LO-ODU in the OTU2. As a result, the transmission apparatus  103  separates the OTU2 from the network  102  into the OTU1, and outputs the OTU1 to each client device  101 . 
     Related techniques are disclosed in, for example, Japanese Laid-Open Patent Publication No. 2011-146917. 
     SUMMARY 
     According to an aspect of the invention, a transmission apparatus includes: a generator configured to generate position information indicating a position of header information of each of a plurality of first signals from a second signal nesting the plurality of first signals; a storage configured to store the position information generated by the generator and the plurality of first signals; a monitor configured to read the position information and the plurality of first signals stored in the storage, and to monitor the header information of each of the plurality of first signals based on the position information; and an output unit configured to output the plurality of first signals after monitoring the contents of the header information. 
     The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is an explanatory diagram illustrating an example of a transmission system according to a present embodiment; 
         FIG. 2  is a block diagram illustrating an example of an ADM of the present embodiment; 
         FIG. 3  is an explanatory diagram illustrating an example of a shared storage unit; 
         FIG. 4  is an explanatory diagram illustrating an example of a format configuration of the OTU; 
         FIG. 5  is an explanatory diagram illustrating an example of control information of an OTU1 I/F; 
         FIG. 6  is a flowchart illustrating an example of a processing operation of the OTU1 I/F relating to an OTU1 I/F process; 
         FIG. 7  is a flowchart illustrating an example of a processing operation of an OTU monitor unit relating to an OTU OH monitoring process; 
         FIG. 8A  is an explanatory diagram illustrating an example of the control information during the reading of the OTU monitor unit; 
         FIG. 8B  is an explanatory diagram illustrating an example of the control information during the writing of the OTU monitor unit; 
         FIG. 9  is a flowchart illustrating an example of a processing operation of an ODU monitor unit relating to an ODU OH monitoring process; 
         FIG. 10A  is an explanatory diagram illustrating an example of the control information during the reading of the ODU monitor unit; 
         FIG. 10B  is an explanatory diagram illustrating an example of the control information during the writing of the ODU monitor unit; 
         FIG. 11  is a flowchart illustrating an example of a processing operation of an ODU insertion unit relating to an ODU OH insertion process; 
         FIG. 12A  is an explanatory diagram illustrating an example of the control information during the reading of the ODU insertion unit; 
         FIG. 12B  is an explanatory diagram illustrating an example of the control information during the writing of the ODU insertion unit; 
         FIG. 13  is a flowchart illustrating an example of a processing operation of the XC  20  relating to an XC process; and 
         FIG. 14  is an explanatory diagram illustrating an example of a transmission system. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     In the transmission apparatus  103  corresponding to OTU1×4 and OTU2×1 illustrated in  FIG. 14 , the contents of the ODU OH are monitored for each LO-ODU process that outputs the HO-ODU to up to eight LO-ODUs. For example, in order to shift the data of the LO-ODU so as to ensure the synchronization of the data of the LO-ODU for each LO-ODU process, OH processing units are provided in the transmission apparatus  103  including registers corresponding to the number of latency of data×number of parallel data. 
     Further, in the transmission apparatus  103 , the ODU processing unit  114  includes the OH processing units having registers for shifting the data of the ODU for each LO-ODU process of separating the data of the LO-ODU from the HO-ODU in order to rewrite a part or all of the ODU OH. 
     Furthermore, the transmission apparatus  103 , for each OTU1 I/F  111 , includes an OH processing unit having registers for shifting the data of each OTU1 until the monitoring of the contents of the OTU OH for each OTU1 is completed when transmitting the OTU1 as the OTU2. Therefore, since a register is required for each OH process, the circuit scale becomes large. 
     Hereinafter, an embodiment of a transmission apparatus and a transmission method in which the circuit scale required for the OH processing is suppressed will be described in detail with reference to the accompanying drawings. The present embodiment is not intended to limit the disclosure. Examples of the embodiment described below may be adequately combined as long as the combination causes no contradiction. 
     Embodiment 
       FIG. 1  is an explanatory diagram illustrating an example of a transmission system of the present embodiment. A transmission system  1  illustrated in  FIG. 1  includes a wide area network (WAN)  2  of an OTN side, and a WAN  3  of a synchronous optical network/synchronous digital hierarchy (SONET/SDH) side. Further, the transmission system  1  includes a local area network (LAN)  4  of an Ethernet (registered trademark) side. In the WAN  2  of the OTN side, a plurality of transmission apparatuses, such as a plurality of optical wavelength multiplexers (hereinafter, simply referred to as “ADM”: add drop multiplexer)  5  are connected. In the WAN  3  of the SONET/SDH side, a plurality of ADMs  9  are connected. 
     In the LAN  4 , a plurality of layer2 switches (L2SWs)  7  for connection with clients  6  are connected. The ADM  5  in the WAN  2  of the OTN side is connected, through the client network  9 A, to an aggregate switch (ASW)  8  or the L2SW  7  in the LAN  4  to relay communication between the client  6  and the WAN  2 . 
       FIG. 2  is a block diagram illustrating an example of the ADM  5 . The ADM  5  illustrated in  FIG. 2  is, for example, connected between client devices  9 A of an OTU1 and a network  9 B of an OTU2. The client devices  9 A may be recited as devices coupling with the client network  9 A. The ADM  5  has four ports that are connected to four client devices  9 A of the OTU1 side, and one port that is connected to the network  9 B of the OTU2 side. The ADM  5  is a transmission apparatus responding to OTU1×4 ports and OTU2×1 port. 
     The ADM  5  includes first clock transfers  11 , OTU1_I/Fs  12 , ODU1_MUXs  14 A, a shared storage unit  13 , an ODU2_MUX  14 B, an OTU2_I/F  15 , and a second clock transfer  16 . Further, the ADM  5  includes an OTU OH processing unit  17 , an ODU_DMUX  18 , an ODU_OH processing unit  19 , and a XC  20 . 
     The first clock transfer  11  changes the clock speed of a signal interfacing between the client device  9 A and the ADM  5 . The OTU1_I/F  12  is a communication I/F between the client device  9 A and the ADM  5 . The second clock transfer  16  changes the clock speed of a signal interfacing between the network  9 B and the ADM  5 . The OTU2_I/F  15  is a communication I/F between the network  9 B and the ADM  5 . Further, it is assumed that an internal clock of the ADM  5  is a clock having a speed higher than those of the client clock of the client device  9 A of the OTU1 and the network clock of the network  9 B of the OTU2. 
     The shared storage unit  13  is constituted, for example, by a plurality of RAMs  21  of a first RAM  21 A to a fifth RAM  21 E. The shared storage unit  13  is a work area for executing processes of the OTU_OH processing unit  17 , the ODU_DMUX  18 , the ODU_OH processing unit  19 , and the XC  20 . 
     The OTU_OH processing unit  17  executes an OH processing for the OTU OH of the OTU1 of the OTU1_I/F  12  while executing an OH processing for the OTU OH of the OTU2 of the OTU2_I/F  15 . The OTU_OH processing unit  17  includes an OTU monitor unit  17 A to monitor the contents of the OTU OH of the OTU1 or OTU2. The ODU_DMUX  18  has a DMUX function of demultiplexing the data of the LO-ODU from the HO-ODU. The ODU_OH processing unit  19  executes an OH processing to insert the contents of the ODU OH while monitoring the contents of the ODU OH of the LO-ODU. The XC  20  rearranges and outputs the data of the LO-ODU to a predetermined output destination on a LO-ODU basis of the ODU_DMUX  18 . The ODU_OH processing unit  19  includes an ODU monitor unit  19 A and an ODU insertion unit  19 B. The ODU monitor unit  19 A monitors the contents of the ODU OH. The ODU insertion unit  19 B inserts the contents of the ODU OH, and upon detecting a rewrite request for rewriting a part or all of the contents of the ODU OH, rewrites a part or all of the contents of the ODU OH. 
     The ADM  5  includes four first clock transfers  11 , four OTU1_I/Fs  12 , and four ODU1_MUXs  14 A for connection with four client devices  9 A. Further, the ADM  5  includes one OTU2_I/F  15  and one ODU2 MUX for connection with the network  9 B. 
       FIG. 3  is an explanatory diagram illustrating an example of the shared storage unit  13 . The shared storage unit  13  illustrated in  FIG. 3  includes a first RAM  21 A, a second RAM  21 B, a third RAM  21 C, a fourth RAM  21 D, a fifth RAM  21 E, a switching controller  22 . The switching controller  22  is switchably connected between the first RAM  21 A to fifth RAM  21 E and the OTU monitor unit  17 A, the ODU_DMUX  18 , the ODU monitor unit  19 A, the ODU insertion unit  19 B and the XC  20 . The switching controller  22  sequentially switches the RAM  21  used for each process of the OTU monitor unit  17 A, the ODU DMUX  18 , the ODU monitor unit  19 A, the ODU insertion unit  19 B, and the XC  20  to an unused RAM  21 . 
       FIG. 4  is an explanatory diagram illustrating an example of a format configuration of the OTU. An OTU  30  illustrated in  FIG. 4  has an OH area  31 , a payload area  32 , and an FEC area  33 . The OH area  31  has a frame size of 16 bytes from first column to 16th column×4 rows. The payload area  32  has a frame size of 3808 bytes from 17th column to 3824th column×4 rows. The FEC area  33  has a frame size of 256 bytes from 3825th column to 4080th column×4 rows. 
     The OH area  31  has a frame alignment OH of the first column to 7th column of the first row, an OTU OH of the 8th column to 14th column of the first row, an ODU OH of the first column to 14th column of the second row to the fourth row, and an OPU OH of the 15th column and 16th column of the first row to the fourth row. The OTU OH is an OH area of the OTU. The ODU OH is an OH area of the ODU. The OPU OH is an OH area of the OPU. 
     The frame alignment OH includes a frame alignment signal (FAS) and a multi-frame alignment signal (MFAS). The FAS is a frame synchronization signal. The MFAS is a multi-frame synchronization signal for detecting a multi-frame synchronization. The OTU OH has section monitoring (SM), general communication channel 0 (GCC0), and reserved for future international standardization (RES). The SM is information indicating a monitoring state between OTU termination points. The GCC0 is information for supporting a communication channel between OTU termination points. 
     The ODU OH has two RESs, tandem connection monitoring activation (TCMACT), TCM1 to TCM6, fault type and fault location reporting channel (FTFL), path monitoring (PM), and experimental (EXP). Also, the ODU OH has GCC1 and GCC2 and an automatic protection switching/protection communication control (APS/PCC) channel. The TCMACT is information for identifying whether a tandem connection monitoring is in an active state or not. The FTFL is information for notifying a fault type and fault location. The PM is information for monitoring a path status. The EXP is information for identifying whether it is for a test. The APS/PCC is automatic protection switching and a switching communication channel. 
     The OPU OH has three RESs, three justification controls (JCs), a payload structure identifier (PSI), a negative justification opportunity (NJO), and a positive justification opportunity (PJO). The PSI is information for identifying a payload type. The JC is an adjustment control for adjusting the amount of information in accordance with an increase or decrease of the information in the payload area  32 . The PJO is an area for storing increased data when data in the payload area  32  is increased. In the payload area  32  of the OTU1, a TS1 and a TS2 of the ODU0 are stored alternately. 
     Upon detecting the synchronization of the OTU1, the OTU1 I/F  12  generates data of each byte in the OTU1 and control information including the properties corresponding to the data, based on the OTU OH of the OTU1.  FIG. 5  is an explanatory diagram illustrating an example of control information  40  of the OTU1 I/F. The control information  40  illustrated in  FIG. 5  associates data of one byte with the properties corresponding to the data. The control information  40  includes an address  41 , data  42 , data enable  43 , payload enable  44 , and an OH count value  45  to be managed in association with each other. Further, the properties include, for example, the data enable  43 , the payload enable  44 , and the OH count value  45 . Further, the control information  40  manages the control information (data and properties) of the ODU0 (TS1) and the control information (data and properties) of the ODU0 (TS2) for each address  41 . 
     The address  41  is position information that identifies a data storage position in the RAM  21 . The data  42  is data of one byte in the OTU. The data enable  43  is an identifier for identifying whether data of one byte is valid data, which is “1” when the data is valid data, and “0” when the data is invalid data. 
     The payload enable  44  is an identifier for identifying whether data of one byte is in the payload area  32 , which is “1” when the data is in the payload area  32 , and “0” when the data is outside the payload area  32 . The OH count value  45  is information for identifying data of one byte with a count number from the head position (first row, first column) of the OH. 
     The ADM  5 , by referring to the address  41  from “2” to “9” illustrated in  FIG. 5 , may be able to identify the data of the OTU1 in which the data enable  43  is “1,” the payload enable  44  is “0,” and the OH count value  45  is “0” to “15” from the OH area  31 . Further, the ADM  5 , by referring to address  41  equal to or greater than “10”, may be able to identify the data of the OTU1 from the payload area  32  because the data enable  43  is “1” and the payload enable  44  is “1.” 
     Further, the OTU monitor unit  17 A monitors the contents of the OTU OH of the SM from the 8th column to 14th column of the first row, and detects a section error by comparing, for example, calculated values and received values of the items of the SM. 
     The ODU monitor unit  19 A monitors the contents of the ODU OH of, for example, the first column to 14th column of the second row, the first column to 14th column of the third row, and the first column to 14th column of the fourth row, and compares received values and expected values, for example, for the FTFL. 
     The ODU insertion unit  19 B replaces a transmission value with the item of TCM6, for example, when the TCM6 is TTI. Also, the ODU insertion unit  19 B replaces a transmission value with the item of FTFL, for example, in the case of FTFL. Further, the ODU insertion unit  19 B, when transmitting an alarm transfer process, stores the control information to the unused RAM  21  to not only rewrite the contents of the ODU OH, but also replace an alarm transfer or test signal or the like with the payload area  32 . 
     Next, an operation of the ADM  5  of the present embodiment will be described. For example, a description will be given on the operation of the ADM  5  when transmitting the OTU1 from each client device  9 A to the network  9 B in the OTU2. 
     The first clock transfer  11  transfers a client clock of the OTU1 from the client device  9 A to an internal clock of the ADM  5 . The OTU1_I/F  12  detects the synchronization based on the FAS of the OTU OH of the OTU1 which has been transferred to the internal clock. The OTU1_I/F  12  generates the control information  40  from the OTU1. The OTU1_I/F  12  generates the properties for each byte of the OTU1, and stores the control information  40  including the data and the properties of each byte of the OTU1 in the unused RAM  21 , for example, the first RAM  21 A, in the shared storage unit  13 . Further, the control information  40  of a total of four OTU1s from each OTU1_I/F  12  is stored in the first RAM  21 A. Further, the RAM  21  becomes a writable unused RAM  21  because the control information  40  is eliminated from the RAM  21  when reading the control information  40 . 
     The OTU monitor unit  17 A of the OTU_OH processing unit  17  reads the control information  40  stored in the first RAM  21 A, and monitors the contents of the OTU_OH of each OTU1 based on the data and the properties of the OTU1 in the read control information  40 . The OTU monitor unit  17 A stores the control information  40  in the unused RAM  21  such as, for example, the second RAM  21 B. Further, the control information  40  of a total of four OTU1s is stored in the second RAM  21 B. 
     The ODU_DMUX  18  separates each OTU1 of the control information  40  read from the second RAM  21 B into the data of each ODU0, and stores the control information  40  including the data of each ODU0 in the unused RAM  21  such as, for example, the third RAM  21 C. Further, the control information  40  of a total of eight ODU0s is stored in the third RAM  21 C. 
     The ODU monitor unit  19 A of the OTU_OH processing unit  19  reads the control information  40  stored in the third RAM  21 C, and monitors the contents of the OTU OH of each OTU0 based on the data and the properties of the OTU1 in the read control information  40 . The ODU monitor unit  19 A stores the control information  40  in the unused RAM  21  such as, for example, the fourth RAM  21 D. Further, the control information  40  of a total of eight ODU0s is stored in the fourth RAM  21 D. 
     The ODU insertion unit  19 B of the OTU_OH processing unit  19  reads the control information  40  stored in the fourth RAM  21 D, and determines whether a rewrite request of the ODU OH has been detected. When a rewrite request of the ODU OH of the ODU0 has been detected, the ODU insertion unit  19 B rewrites the contents of the ODU OH of the ODU0 to update the contents of the rewritten ODU OH. The ODU insertion unit  19 B stores the control information  40  including the data of the updated ODU OH in the unused RAM  21  such as, for example, the fifth RAM  21 E. Further, the control information  40  of a total of eight ODU0s is stored in the fifth RAM  21 E. 
     The XC  20  reads each of the total of eight ODU0s in the control information  40  stored in the fifth RAM  21 E, rearranges the data of each ODU0 to a predetermined output destination, and outputs the data of each ODU0 to the ODU2_MUX  14 B. The ODU2_MUX  14 B stores the data of eight ODU0s in the ODU2, and outputs the ODU2 to the OTU2_I/F  15  while being stored in the OTU2. The OTU2_I/F  15  inserts the FEC value into the FEC area  33  of the OTU2 while inserting the OTU OH into the OH area  31  of the OTU2. Further, the OTU2_I/F  15  outputs the OTU2 to the second clock transfer  16 . The second clock transfer  16  transfers the OTU2 from the internal clock of the ADM  5  to the network clock, and outputs the OTU2 to the network  9 B. 
     Next, an operation of the ADM  5  when transmitting the OTU2 from the network  9 B as the OTU1 to each client device  9 A will be described. 
     The second clock transfer  16  transfers the network clock of the OTU2 from the network  9 B to the internal clock in the ADM5. The OTU2_I/F  15  detects the synchronization based on the FAS of the OTU OH of the OTU2 which has been transferred to the internal clock. The OTU2_I/F  15  generates the control information  40  from the OTU2. The OTU2_I/F  15  generates the properties for each byte of the OTU2, and stores the control information  40  including the data and the properties of each byte of the OTU2 in the unused RAM  21  such as, for example, the first RAM  21 A, in the shared storage unit  13 . Further, the control information  40  of one OTU2 from the OTU2_I/F  15  is stored in the first RAM  21 A. 
     The OTU monitor unit  17 A reads the control information  40  of the OTU2 stored in the first RAM  21 A, and monitors the contents of the OTU OH in the OTU2 based on the data and the properties of the OTU2 in the read control information  40 . The OTU monitor unit  17 A stores the control information  40  in the unused RAM  21  such as, for example, the second RAM  21 B. Further, the control information  40  of one OTU2 is stored in the second RAM  21 B. 
     The ODU_DMUX  18  separates the OTU2 of the control information  40  read from the second RAM  21 B into the data of eight ODU0s, and stores the control information  40  including each ODU0 in the unused RAM  21  such as, for example, the third RAM  21 C. Further, the control information  40  of a total of eight ODU0s is stored in the third RAM  21 C. 
     The ODU monitor unit  19 A reads the control information  40  stored in the third RAM  21 C, and monitors the contents of the ODU OH of each ODU0 based on the data and the properties of the ODU0 in the read control information  40 . The ODU monitor unit  19 A stores the control information  40  in the unused RAM  21  such as, for example, the fourth RAM  21 D. Further, the control information  40  of a total of eight ODU0s is stored in the fourth RAM  21 D. 
     The ODU insertion unit  19 B reads the control information  40  stored in the fourth RAM  21 D, and determines whether a rewrite request of the ODU OH has been detected. The rewrite request is, for example, an update request. When a rewrite request of the ODU OH of the ODU0 has been detected, the ODU insertion unit  19 B rewrites the contents of the ODU OH of the corresponding ODU0 to update the contents of the rewritten ODU OH. The ODU insertion unit  19 B stores the control information  40  including the data of the updated ODU OH in the unused RAM  21  such as, for example, the fifth RAM  21 E. Further, the control information  40  of a total of eight ODU0s is stored in the fifth RAM  21 E. 
     The XC  20  reads each of the total of eight ODU0s in the control information  40  stored in the fifth RAM  21 E, rearranges each ODU0 to a predetermined output destination, and outputs the data of each ODU0 to the ODU1_MUX  14 A. The ODU1_MUX  14 A stores two ODU0s in the ODU1, and outputs the ODU1 to the OTU1_I/F  12  while storing in the payload area  32  of the OTU1. The OTU1_I/F  12  inserts the FEC value into the FEC area  33  of the OTU1 while inserting the OTU OH into the OH area  31  of the OTU1. Further, the OTU1_I/F  12  outputs the OTU1 to the first clock transfer  11 . The first clock transfer  11  transfers the OTU1 from the internal clock to the client clock, and outputs the OTU1 to the client device  9 A. 
     As described above, the ADM  5  monitors the contents of the OTU OH of the OTU1 by using the data and the properties of each OTU1 stored in a single RAM  21 . As a result, since four registers may be shared by a single RAM  21  as in the conventional case, it is possible to suppress the circuit scale. 
     The ADM  5  monitors the contents of the ODU OH of the ODU0 by using the data and the properties of each ODU0 stored in a single RAM  21 . As a result, since eight registers may be shared by a single RAM  21  as in the conventional case, it is possible to suppress the circuit scale. 
     Upon detecting a rewrite request of the ODU OH of the ODU0, the ADM  5  rewrites the contents of the ODU OH of the ODU0 by using the data of each ODU0 stored in a single RAM  21 . As a result, since eight registers may be shared by a single RAM  21  as in the conventional case, it is possible to suppress the circuit scale. 
       FIG. 6  is a flowchart illustrating an example of a processing operation of the OTU1_I/F  12  relating to an OTU1 I/F process. The OTU1 I/F process illustrated in  FIG. 6  is a process of storing the control information  40  including the data and the properties of each byte of the OTU1 in the unused RAM  21  when receiving the OTU1. 
     The OTU1_I/F  12  determines whether the OTU1 has been received (operation S 11 ). When it is determined that the OTU1 has been received (“Yes” in operation S 11 ), the OTU1_I/F  12  determines whether the synchronization of the OTU1 has been detected based on the FAS of the OTU OH of the OTU1 (operation S 12 ). 
     The OTU1_I/F  12  generates the properties corresponding to the data of each byte of the OTU1 (operation S 13 ). Further, the OTU1_I/F  12  generates the data enable  43 , the payload enable  44 , and the OH count value  45  for each data of one byte. The OTU1_I/F  12  stores the control information  40  including the data and the properties of each byte of the OTU1 in the unused RAM  21  (operation S 14 ), and ends the processing operation illustrated in  FIG. 6 . 
     When it is determined that the OTU1 has not been received (“No” in operation S 11 ), the OTU1_I/F  12  ends the processing operation illustrated in  FIG. 6 . When it is determined that the synchronization of the OTU1 has not been detected (“No” in operation S 12 ), the OTU1 I/F  12  proceeds to operation S 12  in order to monitor whether the synchronization of the OTU1 has been detected. 
     In the OTU1 I/F process illustrated in  FIG. 6 , when receiving the OTU1, the data and the properties of each byte are generated based on the data in the OTU1, and the control information  40  including the data and the properties of each byte is stored in the RAM  21 . 
     Further, in the OTU1 I/F process illustrated in  FIG. 6 , the control information  40  of the OTU1 is generated by using the OTU1_I/F  12 , and the control information  40  is stored in the RAM  21 , but it is also applicable to the OTU2_I/F  15 . In this case, the control information  40  of the OTU2 may be generated and the control information  40  may be stored in the RAM  21 . 
       FIG. 7  is a flowchart illustrating an example of a processing operation of the OTU monitor unit  17 A relating to an OTU OH monitoring process. The OTU OH monitoring process illustrated in  FIG. 7  is a process of monitoring the contents of the OTU OH in each OTU1 based on the control information  40  stored in the RAM  21 . 
     The OTU monitor unit  17 A reads the control information  40  including the data and the properties of the OTU1 stored in the RAM  21  (operation S 21 ), and refers to the data enable  43  and the payload enable  44  of the properties for each specified data. Further, the specified data are sequentially designated for each data  42  of the OTU1 of the control information  40 . The OTU monitor unit  17 A determines whether the data enable  43  of the specified data is “1” and the payload enable  44  of the specified data is “0” (operation S 22 ). 
     The OTU monitor unit  17 A determines that the specified data is considered as valid data in the OH area  31  when it is determined that the data enable  43  of the specified data is “1” and the payload enable  44  of the specified data is “0” (“Yes” in operation S 22 ). Further, when it is determined that the specified data is valid data in the OH area  31 , the OTU monitor unit  17 A checks the contents of the OTU OH based on the OH count value  45  of the specified data (operation S 23 ). Further, the OTU monitor unit  17 A may identify the contents of the OTU OH of the specified data based on the OH count value  45 . 
     After checking the contents of the OTU OH of the specified data, the OTU monitor unit  17 A determines whether the OH count value  45  of the specified data exceeds a first OH threshold (operation S 24 ). Further, the first OH threshold corresponds to an OH count value greater than the OH head (first row, first column) to the 14th column of the first row, and is, for example, an area of the ODU OH of the 15th column of the first row. 
     When it is determined that the OH count value  45  of the specified data exceeds the first OH threshold (“Yes” in operation S 24 ), the OTU monitor unit  17 A determines whether there is a staff process (operation S 25 ). Further, the OTU monitor unit  17 A determines whether there is a staff process by majority processing of three JCs in the OPU OH. 
     When it is determined that there is a staff process (“Yes” in operation S 25 ), the OTU monitor unit  17 A executes a staff process of writing staff data in the payload area  32  of the OTU1 (operation S 26 ). The OTU monitor unit  17 A rewrites the contents of the data enable  43  and the payload enable  44  based on the execution result of the staff process, and updates the control information  40  (operation S 27 ). Furthermore, after updating the control information  40 , the OTU monitor unit  17 A stores the control information including the data and the properties of each byte of the OTU1 in the unused RAM  21  (operation S 28 ), and ends the processing operation illustrated in  FIG. 7 . 
     When it is determined that the data enable  43  of the specified data is not “1” and the payload enable  44  of the specified data is not “0” (“No” in operation S 22 ), the OTU monitor unit  17 A determines whether the OH count value  45  of the specified data exceeds the first OH threshold, and proceeds to operation S 24 . 
     When it is determined that the OH count value  45  of the specified data does not exceed the first OH threshold (“No” in operation S 24 ), the OTU monitor unit  17 A determines that the specified data is in the OH area  31 . When it is determined that the specified data is in the OH area  31 , the OTU monitor unit  17 A determines whether the data enable  43  of the specified data is “1” and the payload enable  44  of the specified data is “0,” and proceeds to operation S 22 . 
     When it is determined that there is no staff process (“No” in operation S 25 ), the OTU monitor unit  17 A stores the control information  40  in the unused RAM  21 , and proceeds to operation S 28 . 
     The OTU monitor unit  17 A reads the control information  40  stored in the RAM  21 , and monitors the contents of the OTU OH of the specified data based on the OH count value  45  if the specified data is valid data in the OH area  31 . As a result, even without providing a register for each OTU1 I/F as in the conventional case, the OTU monitor unit  17 A reads the control information  40  stored in a single RAM  21 , and checks the contents of the OTU OH of each OTU1. 
     Further, when it is determined that there is a staff process, the OTU monitor unit  17 A executes the staff process, updates the control information  40  by performing the rewriting of the data and the properties, and stores the updated control information  40  in the unused RAM  21 . As a result, even without providing a register for each OTU1 I/F as in the conventional case, the OTU monitor unit  17 A reads the control information  40  stored in a single RAM  21  and updates the payload area of each OTU1 when it is determined that there is a staff process. 
       FIG. 8A  is an explanatory diagram illustrating an example of the control information  40  during the reading of the OTU monitor unit  17 A.  FIG. 8B  is an explanatory diagram illustrating an example of the control information  40  during the writing of the OTU monitor unit  17 A. As illustrated in  FIGS. 8A and 8B , the OTU monitor unit  17 A rewrites “0” of the data enable  43  of the TS2 of “xxx” of the address  41  to “1” by the staff process. 
       FIG. 9  is a flowchart illustrating an example of the processing operation of the ODU monitor unit  19 A relating to the ODU OH monitoring process. The ODU OH monitoring process illustrated in  FIG. 9  is a process of monitoring the contents of the ODU OH of the ODU0 for each LO-ODU based on the control information  40  stored in the RAM  21 . 
     The ODU monitor unit  19 A reads the control information  40  stored in the RAM  21  (operation S 31 ), and determines whether the data enable  43  of the specified data is “1” and the payload enable  44  of the specified data is “1” (operation S 32 ). When it is determined that the data enable  43  of the specified data is not “1” and the payload enable  44  of the specified data is not “1” (“No” in operation S 32 ), the ODU monitor unit  19 A determines that the specified data is not in the OH area  31 , and ends the processing operation illustrated in  FIG. 9 . When it is determined that the data enable  43  of the specified data is “1” and the payload enable  44  of the specified data is “1” (“Yes” in operation S 32 ), the ODU monitor unit  19 A determines whether the synchronization of the ODU0 has been detected based on the FAS of the ODU OH of the ODU0 in the control information  40  (operation S 33 ). 
     When it is determined that the synchronization of the ODU0 has been detected (“Yes” in operation S 33 ), the ODU monitor unit  19 A rewrites the properties corresponding to the data of each byte in the ODU0 (operation S 34 ). 
     After the processing of operation S 34 , the ODU monitor unit  19 A checks the contents of the ODU OH based on the OH count value  45  of the specified data (operation S 35 ). Further, the ODU monitor unit  19 A may be able to identify the contents of the ODU OH of the specified data based on the OH count value  45 . 
     After checking the contents of the ODU OH of the specified data, the ODU monitor unit  19 A determines whether the OH count value  45  of the specified data exceeds a second OH threshold (operation S 36 ). Further, the ODU OH is the first column to 14th column of the second row, the first column to 14th column of the third row, and the first column to 14th column of the fourth row in the OTU frame. The second OH threshold is, for example, an OH count value greater than the head position (first column of the first row) of the OH to the 14th column of the fourth row. 
     When it is determined that the OH count value  45  of the specified data exceeds the second OH threshold (“Yes” in operation S 36 ), the ODU monitor unit  19 A stores the control information  40  in the unused RAM  21  (operation S 37 ), and ends the processing operation illustrated in  FIG. 9 . 
     When it is determined that the synchronization of the ODU0 has not been detected (“No” in operation S 33 ), the ODU monitor unit  19 A determines whether the synchronization of the ODU0 has been detected, and proceeds to operation S 33 . 
     When it is determined that the OH count value  45  does not exceed the second OH threshold (“No” in operation S 36 ), the ODU monitor unit  19 A proceeds to operation S 32 . 
     The ODU monitor unit  19 A reads the control information stored in the RAM  21 , and when the specified data is valid data in the OH area  31 , checks the contents of the ODU OH of the specified data based on the OH count value  45 . As a result, even without providing a register for each LO-ODU as in the conventional case, the OTU monitor unit  17 A reads the control information  40  stored in a single RAM  21 , and checks the contents of the ODU OH of each ODU0. 
       FIG. 10A  is an explanatory diagram illustrating an example of the control information during the reading of the ODU monitor unit  19 A.  FIG. 10B  is an explanatory diagram illustrating an example of the control information during the writing of the ODU monitor unit  19 A. The ODU monitor unit  19 A rewrites the payload enable  44  and the OH count value  45  of the TS1 and TS2 at “10” and after of the address  41  to change the control information from  FIGS. 10A to 10B . Further, the ODU monitor unit  19 A rewrites the data enable  43  of the TS1 and TS2 at “2” to “9” of the address  41  to “0” to change the control information from  FIGS. 10A to 10B . 
       FIG. 11  is a flowchart illustrating an example of a processing operation of the ODU insertion unit  19 B relating to an ODU OH insertion process. The ODU OH insertion process illustrated in  FIG. 11  is a process of rewriting the contents of the ODU OH upon detecting a rewrite request from the contents of the ODU OH of each ODU0 for each LO-ODU based on the control information  40  stored in the RAM  21 . 
     The ODU insertion unit  19 B in  FIG. 11  reads the control information  40  stored in the RAM  21  (operation S 41 ), and determines whether the data enable  43  of the specified data is “1” and the payload enable  44  of the specified data is “0” (operation S 42 ). 
     The ODU insertion unit  19 B determines that the specified data is valid data in the ODU OH when it is determined that the data enable  43  of the specified data is “1” and the payload enable  44  of the specified data is “0” (“Yes” in operation S 42 ). Further, when it is determined that the specified data is valid data in the ODU OH, the ODU insertion unit  19 B checks the contents of the ODU OH based on the OH count value  45  (operation S 43 ). 
     The ODU insertion unit  19 B determines whether a rewrite request of the contents of the ODU OH has been detected (operation S 44 ). When a rewrite request of the contents of the ODU OH has been detected (“Yes” in operation S 44 ), the ODU insertion unit  19 B rewrites the contents of the ODU OH of the rewrite request (operation S 45 ). As a result, the ODU insertion unit  19 B generates the properties according to the rewriting of the contents of the ODU OH. The ODU insertion unit  19 B determines whether the OH count value  45  exceeds the second OH threshold (operation S 46 ). 
     When it is determined that the OH count value  45  exceeds the second OH threshold (“Yes” in operation S 46 ), the ODU insertion unit  19 B stores the control information  40  in the unused RAM  21  (operation S 47 ), and ends the processing operation illustrated in  FIG. 11 . 
     When it is determined that the OH count value  45  does not exceed the second OH threshold (“No” in operation S 46 ), the ODU insertion unit  19 B determines whether the data enable  43  of the specified data is “1” and the payload enable  44  of the specified data is “0,” and proceeds to operation S 42 . 
     When it is determined that the data enable  43  of the specified data is not “1” and the payload enable  44  of the specified data is not “0” (“No” in operation S 42 ), the ODU insertion unit  19 B determines whether the OH count value  45  exceeds the second OH threshold, and proceeds to operation S 46 . When it is determined that a rewrite request of the contents of the ODU OH has not been detected (“No” in operation S 44 ), the ODU insertion unit  19 B determines whether the OH count value  45  exceeds the second OH threshold, and proceeds to operation S 46 . 
     The ODU insertion unit  19 B in  FIG. 11  reads the control information  40  stored in the RAM  21 , and upon detecting a rewrite request of the contents of the ODU OH, rewrites the contents of the ODU OH for each LO-ODU. As a result, the ODU insertion unit  19 B is able to read the control information  40  stored in a single RAM  21  and updates the contents of the ODU OH of each ODU0 without requiring a register for each LO-ODU as in the conventional case. 
       FIG. 12A  is an explanatory diagram illustrating an example of the control information during the reading of the ODU insertion unit  19 B.  FIG. 12B  is an explanatory diagram illustrating an example of the control information during the writing of the ODU insertion unit  19 B. The ODU insertion unit  19 B rewrites and updates the data by rewriting the contents of the ODU OH, and does not change the contents of the properties as illustrated in  FIGS. 12A and 12B . 
       FIG. 13  is a flowchart illustrating an example of a processing operation of the XC  20  relating to an XC processing. The XC processing illustrated in  FIG. 13  is a process of reading the control information  40  stored in the RAM  21  and rearranging each ODU0 to a predetermined output destination. 
     As illustrated in  FIG. 13 , the XC  20  reads the control information  40  from the RAM  21  (operation S 51 ), rearranges each ODU0 to a predetermined output destination (operation S 52 ), outputs the data for each ODU0 from the output destination to the ODU2 MUX  14 B (operation S 53 ), and ends the processing operation. 
     In  FIG. 13 , the XC  20  reads the control information  40  stored in the RAM  21 , rearranges the data of each ODU0 to a predetermined output destination, and outputs the rearranged ODU0 to the ODU2 MUX  14 B. 
     The OTU monitor unit  17 A of the ADM  5  of the present embodiment generates the properties indicating the position of each OH from the OTU1 storing a plurality of ODU0s, and sequentially stores the data and the OH position of each OTU1 in a single unused RAM  21 . The ODU monitor unit  19 A reads the properties and the data of each ODU0 stored in a single RAM  21 , and checks the contents of the ODU OH of the read data of each ODU0. As a result, even without providing a register for each LO-ODU as in the conventional case, the ODU monitor unit  19 A is able to read each ODU0 and the properties stored in a single RAM  21 , and checks the contents of the ODU OH of each ODU0. 
     Upon detecting a rewrite request of the ODU OH of the ODU0 stored in the RAM  21 , the ODU insertion unit  19 B of the ADM  5  updates the contents of the ODU OH of the ODU0 stored in the RAM  21  to update the ODU0 in a single RAM  21 . As a result, without requiring a register for each LO-ODU as in the conventional case, the ODU insertion unit  19 B is able to read each ODU0 and the properties stored in a single RAM  21  and update the contents of the ODU OH of each ODU0. 
     The ADM  5  transfers the clock to the internal clock between the ADM  5  and the client device  9 A of the OTU1 in the first clock transfer  11 , and at the same time, transfers the clock to the internal clock between the ADM  5  and the network  9 B of the OTU2 in the second clock transfer  16 . As a result, in the ADM  5 , since different clocks of the OTU are transferred to a common internal clock, there is no asynchronous part inside the apparatus, and for example, loop-back of data is easily carried out by smoothly performing the separation and multiplexing process of the OTU. 
     In a conventional ADM, for example, four FPGAs having a 360 k gate size are employed when performing a LO-ODU process for eight ports. In contrast, in the ADM  5  of the present embodiment, since the RAM  21  is used, it is implemented with one FPGA having a 500 k gate size. 
     Although the number of the RAMs  21  is five in the above embodiment, it is not limited to five, but at least one RAM  21  may be provided. For convenience of explanation, it has been described in the above embodiment that the control information is read from the first RAM  21 A, and stored in the unused second RAM  21 B when processing the read control information. However, it is not limited to the second RAM  21 B, and it may be an unused RAM. 
     In the above embodiment, the ADM  5  corresponding to OTU1-OTU2 has been exemplified, but it is not limited thereto, and may be applied to the ADM  5  corresponding to OTU1-OTU3, an OTU combination pattern or the like. 
     In the above-described embodiment, the client device  2  of the OTU1 has been exemplified as a client device, but it is not limited to the OTU, and it may be connected to, for example, a client device such as a LAN and SON ET. 
     Further, in the ADM  5  of the above-described embodiment, an OTU in which the LO-ODU is multiplexed by being nested in two stages has been exemplified, but it is not limited to two stages, and is also applicable to an OTU in which the ODU is multiplexed by being nested in three or more stages. 
     In the ADM  5  of the above embodiment, the HO-ODU storing the LO-ODU has been multiplexed by being nested in a plurality of stages, but the combination pattern of ODU types may be appropriately changed. 
     The constituent elements of each part are not necessarily required to be configured physically as illustrated. In other words, a specific mode of distribution and integration of each part is not limited to the illustrated one, and all or a part thereof may be configured to be functionally or physically distributed or integrated as arbitrary units depending on various loads or use conditions. 
     Further, all or a part of various processing functions performed by each device may be executed on a central processing unit (CPU) (or a microcomputer such as a Micro Processing Unit (MPU) and a micro controller unit (MCU)). Further, it goes without saying that all or a part of various processing functions may be executed on a program analyzed and executed by a CPU (or a microcomputer such as MPU and MCU), or on hardware using a wired logic. 
     All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to an illustrating of the superiority and inferiority of the invention. Although the embodiments of the present invention have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.