Abstract:
A technique for distributing highways to a plurality of line cards in an exchange includes: a highway selector for distributing highways necessary for the line cards; and a controller for receiving card information from the line cards, and controlling the highway selector so as to distribute a specific highway to a specific line card.

Description:
CLAIM OF PRIORITY 
     This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from an application for APPARATUS AND METHOD FOR DISTRIBUTING HIGHWAY IN EXCHANGE earlier filed in the Korean Industrial Property Office on Sep. 30, 1997 and there duly assigned Serial No. 50514/1997. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to highways of a PBX (private branch exchange), and more particularly, to a technique for distributing highways to subscriber cards of a PBX. 
     2. Description of the Related Art 
     In general, a PBX is contained within a cabinet. The cabinet has a plurality of shelves therein. Cards for performing various switching functions demanded from the exchange are inserted into respective slots of these shelves. For instance, a card including a circuit for switching a subscriber signal is installed on a control shelf of the exchange, and a card including a circuit for accommodating subscribers is installed on a line shelf. A highway cable is connected between the control shelf and the line shelf. 
     Typically, one highway is comprised of 32 channels each having 8 bits and synchronized with a frame synchronization of 8 KHz. Therefore, a PCM (Pulse Code Modulation) data speed of one highway is 2.048 MHZ (=8 KHZ*8 bits*32 channels). A time switch, which is a PCM switch, uses 8 highways generally, and therefore, it has 256 channels (=32 channels*8). 
     In an earlier highway distribution apparatus in a private branch exchange, a time switch has 8 highways HW 1 , . . . , HW 8 . 16 line cards each have 16 channels and interfacing with the exterior. One highway is connected to two line cards each having 16 channels. 
     According to the number of channels, the line card is classified into a 32-SLI (Single Line Interface Card) using 32 channels, a 16-SLI using 16 channels and an 8-SLI using 8 channels. One highway may be fixedly connected to 2 16-SLIs. However, if the 8-SLI or 32-SLI is actually used, operation may be impossible or the highway channel may bring about a loss. In other words, assuming that the time switch is set to 16 channels per line card, operation is impossible in an ISDN (Integrated Services Digital Network) or an ATM (Asynchronous Transfer Mode) because it needs 64 channels, and there is loss of channels in the 8-SLI. Moreover, if the line card requires 32 channels, only one of two line cards to which one highway is supplied is used, and the other line card can not be used. 
     The following patents each discloses features in common with the present invention but do not teach or suggest the specific technique for distributing highways in an exchange in accordance with the present invention: U.S. Pat. No. 4,796,294 to Nakagawara, entitled Electioonic Telephone Exchange And Method Of Connecting Ports Of The Exchange, U.S. Pat. No. 4,736,409 to Hasegawa et al, entitled Control Data Transmission Systems For Private Branch Exchange, U.S. Pat. No. 4,674,083 to Rachkin, entitled Time Division Multiplexed Switching Structure For PBX, U.S. Pat. No. 4,140,877 to Joslow et al., entitled Multiple Highway Time Division Multiplexed PABX Communication System, U.S. Pat. No. 5,161,155 to Dyer et al., entitled Automatic Telecommunications Systems, U.S. Pat. No. 4,694,452 to Beckinger et al., entitled Switching Configuration For A Telecommunications System In particular A PBX System With Subscriber Lines, Trunk Groups, And Interface Modules, U.S. Pat. No. 5,151,896 to Bowman et al., entitled Modular Digital Telephlone System With Fully Distributed Local Switching And Control, U.S. Pat. No. 5,682,385 to Garcia et al., entitled Enhancement For A Multiplexing Telecommunications Interface, and U.S. Pat. No. 5,581,553 to Cave et al., entitled Distributed Switching Architecture. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a technique for efficiently distributing highways necessary for line cards in an exchange. 
     In one aspect of the present invention, there is provided an apparatus for distributing highways to a plurality of line cards in an exchange, comprising: a highway selector for distributing highways necessary for the line cards; and a controller for receiving card information from the line cards, and controlling the highway selector so as to distribute a specific highway to a specific line card. 
     In another aspect of the present invention, a method for distributing highways to a plurality of line cards by using a highway selector in an exchange, comprises the steps of: reading out card information from the line cards to detect highway channel information; and distributing the highways using the highway selector according to the detected channel information so as to distribute a specific highway to a specific line card. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete appreciation of the invention, and many of the attendant advantages thereof, will be readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference symbols indicate the same or similar components, wherein: 
     FIG. 1 shows an earlier highway distribution apparatus in an exchange; 
     FIG. 2 shows a cabinet of an exchange according to the present invention; 
     FIG. 3 shows highways supplied to each rack of the cabinet of FIG. 2; 
     FIG. 4 shows a highway distribution apparatus according to the present invention; 
     FIG. 5 is a detailed circuit diagram of a highway switch circuit indicated in FIG. 4; 
     FIG. 6 shows a highway protector and a select controller indicated in FIG. 4; and 
     FIG. 7 shows a highway enable signal generated by the select controller illustrated in FIG.  6 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The descriptions of various configurations and components of the present invention which would have been known to one skilled in the art have been omitted for the sake of clarity and brevity. Also, in the figures, similar reference numerals or symbols designate similar elements. 
     FIG. 1 illustrates the earlier highway distribution apparatus discussed in detail in the Description of the Related Art above. 
     A time switch  1  has 8 highways. There are 16 line cards 2, each having 16 channels and interfacing with the exterior. One highway is connected to two line cards, each having 16 channels. 
     Referring to FIG. 2, there is shown a cabinet of an exchange. The cabinet has two racks each having a plurality of line cards SLOT B 1 , . . . , SLOT B 10 . 
     FIG. 3 shows highways supplied to each rack of the cabinet of FIG.  2 . Highways with numbers  2 , . . . ,  7  and  10 , . . . ,  15  are respectively supplied to two racks. Therefore, each rack distributes 6 highways to 10 line cards. 
     Referring to FIG. 4, a highway distribution apparatus includes a time switch  16  having 6 highways, line cards  11 , . . . ,  12  having card information including highway channel information, highway selectors  20 , . . . ,  19 , and a controller  10 . The controller  10  reads out the card information from the line cards  11 , . . . ,  12  and controls the highway selector  20  to distribute the highways. The controller  10 , which is a controller of a system, corresponds to a CCP and an ECP shown in FIG.  2 . The highway selector  20  connected between the time switch  16  and the line card  11  distributes the highways under the control of the controller  10 . The highway selector  20  includes a highway protector  13 , a selection controller  14 , and a highway switch circuit  15 . The highway protector  13  generates an enable signal for enabling the selection controller  14  under the control of the controller  10 . The selection controller  14  receives the enable signal from the highway protector  13  and controls the highway switch circuit  15  under the control of the controller  10  to distribute the highways. 
     FIG. 5 is a detailed circuit diagram of the highway switch circuit  15  shown in FIG.  4 . Transmitting buffers  21 , . . . ,  26  connects the highways to the line cards. Receiving buffers  27 , . . . ,  32  connects the highways to the line cards. Each of the transmitting and receiving buffers  21 , . . . ,  26  and  27 , . . . ,  32  operate by a highway enable signal HWEN generated by the selection controller  14 , and may each use a 74HC125 buffer element. 
     FIG. 6 shows the highway protector  13  and the selection controller  14  indicated in FIG.  4 . The highway protector  13 , using a 74HC74 flip-flop, receives control signals D 1  and HW_PRO from the controller  10  and generates an enable signal for enabling the selection controller  14 . The selection controller  14  operates by the enable signal generated by the highway protector  13 . The selection controller  14  receives control signals D 0 , D 1 , D 2  and /HWSET for selecting the highway and a signal TSX/TSR for selecting the channel from the controller  10  and sends the channel-allocated highway enable signal HWEN to the highway switch circuit  15 . Then the highway switch circuit  15  opens a corresponding buffer to connect the highway to a corresponding line card. The selection controller  14  generates a corresponding address map by using GAL. 
     FIG. 7 shows the highway enable signal generated by the selection controller  14  illustrated in FIG. 6. A highway (HW) uses 32 channels. In order to connect the highway of corresponding channels (T channels) to the line card, the selection controller  14  receives the signal TSX/TSR for selecting the channel from the controller  10  and generates the highway enable signal HWEN. 
     As described above, the highway selector is used to distribute the highway in the exchange. The line card can select the highways irrespective of their number, and one highway can be used for multiple line cards. 
     While the invention has been shown and described with reference to a certain preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.