Abstract:
An short message service switching private branch exchange system and a method can reduce costs. The method can include certifying whether a usable DSP exists or not when an office line and a speech path are connected to each other, and transmitting an short message service signal transmitted from the office line to the DSP through a PCM channel if the usable DSP exists. A main processor of the private branch exchange can certify an extension line terminal that will receive short message service, generate an short message service signal having a format corresponding to a kind of the extension line terminal by using the DSP, and transmit the formatted SMS signal to an extension line interface unit of a corresponding extension line terminal. The system switches an SMS signal between an office line and an extension line by sharing the DSP, for example, by time division.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a private branch exchange (PBX). More particularly, the present invention relates to a digital private branch exchange system for switching a short message service and a switching method.  
           [0003]    2. Background of the Related Art  
           [0004]    Generally, a private branch exchange is an exchange for switching between extension lines in a business site such as an office, a company, a factory, a hotel, etc. or for switching between an extension line and an office line. Methods for providing a short message service (SMS) to users of the extension lines connected to the private branch exchange by using the private branch exchange are being researched.  
           [0005]    [0005]FIG. 1 is a construction view of a related art digital private branch exchange for switching the SMS. As shown in FIG. 1, a digital private branch exchange  10  for switching the SMS converts an SMS signal received through an office line such as a public switched telephone network (PSTN), an integrated services digital network (ISDN), etc. into a format corresponding to an extension line terminal  90  and then switches into the extension line terminal  90 .  
           [0006]    The extension line terminal  90  includes a single line terminal SLT for SMS  92  and a digital terminal  94 . The private branch exchange  10  includes: an analog office line interface unit  20 ; an ISDN office line interface unit  30 ; a voice mail interface unit  40 ; a SLT extension line interface unit  60 ; a digital terminal extension line interface unit  70 ; and a main processor  50 . The units  20 ,  30 ,  40 ,  50 ,  60 , and  70  are connected to one another by an SMS data bus  80 , and the main processor  50  controls SMS data exchange among the units.  
           [0007]    The analog office line interface unit  20  interfaces with an analog office line such as the PSTN. The analog office line interface unit  20  includes an analog office line SMS unit  21  for detecting an SMS signal of a frequency shift keying (FSK) format transmitted through the analog office line and converting the detected SMS signal into SMS data. The SMS data can be data from the analyzed SMS signal.  
           [0008]    The ISDN office line interface unit  30  interfaces with an ISDN office line. The ISDN office line interface unit  30  includes an ISDN office line SMS unit  31  for detecting an SMS signal of a pulse code modulation (PCM) format transmitted through the ISDN office line and converting the detected SMS signal into SMS data.  
           [0009]    The voice mail interface unit  40  provides a voice mail service function. The voice mail interface unit  40  includes a digital signal processor (DSP)  41  for compressing voice and reproducing the compressed voice, and a memory  42  for storing the voice compressed by the DSP  41 .  
           [0010]    The main processor  50  controls the entire private branch exchange  10 . The main processor  50  certifies an extension line terminal that will receive the SMS and transmit the SMS to the corresponding extension line terminal.  
           [0011]    The SLT extension line interface unit  60  connects the SLT  92  and the private branch exchange  10 . The SLT extension line interface unit  60  includes a SLT extension line SMS unit  61  for converting SMS data transmitted from the main processor  50  into an SMS signal of an FSK format. The digital terminal extension line interface unit  70  connects the private branch exchange with the digital terminal  94 , and transmits SMS data transmitted from the main processor  50  to the corresponding digital terminal  94 .  
           [0012]    Operations for switching SMS in the digital private branch exchange  10  will now be described. FIG. 2 shows a method for switching SMS in the digital private branch exchange. As shown in FIG. 2, if a speech path is connected between the private branch exchange  10  and the office line board (the analog office line interface unit  20 ) or the ISDN office line interface unit  30  before the SMS signal is received, the private branch exchange  10  certifies whether a corresponding SMS unit is connected to a corresponding office line board or not (S 12 ).  
           [0013]    If the corresponding SMS unit is not connected to the corresponding office line board, the private branch exchange  10  finishes a procedure for receiving the SMS. However, if the corresponding SMS unit is connected to the corresponding office line board, the private branch exchange  10  finishes signaling for receiving the SMS by using the corresponding SMS unit and then receives the SMS signal (S 14 ). When the corresponding office line board is the analog office line interface unit  20 , the analog office line SMS unit  21  receives an SMS signal of an FSK format, and when the corresponding office line board is the ISDN office line interface unit  30 , the ISDN office line SMS unit  31  receives an SMS signal of pulse code modulation format.  
           [0014]    The corresponding SMS unit which has received the SMS signal converts the SMS signal into SMS data and then transmits to the main processor  50  through the SMS data bus  80 . That is, the analog office line SMS unit  21  converts the SMS of an FSK format into the SMS data, and the ISDN office line SMS unit  31  converts the SMS signal of a PCM format into the SMS data (S 16 ).  
           [0015]    The main processor  50  certifies that a receiving terminal of the SMS is an SLT or a digital terminal on the basis of the received SMS data (S 18 ). If the receiving terminal of the SMS (an extension line terminal which will receive the SMS data) is the SLT  92 , the main processor  50  certifies whether the SLT extension line interface unit  60  connected to the SLT  92  is provided with the SLT extension line SMS unit  61  or not (S 20 ). If the SLT extension line SMS unit is connected to the SLT extension line interface unit  60 , the main processor  50  transmits the SMS data to the SLT extension line interface unit  60  (S 22 ).  
           [0016]    The SLT extension line SMS unit  61  of the SLT extension line interface unit  60  performs signaling with the SLT  92  (S 24 ), and converts the SMS data into an SMS signal of an FSK format then transmits the converted SMS signal of an FSK format to the SLT  92  (S 26 ). Then, the SLT  92  displays the received SMS signal on a display unit.  
           [0017]    However, if the receiving terminal of the SMS (the extension line terminal which will receive the SMS data) is the digital terminal  94  (S 18 ), the main processor  50  transmits the SMS data to the digital terminal extension line interface unit  70  (S 28 ). The digital terminal extension line interface unit  70  transmits the SMS data to the corresponding digital terminal  94  (S 30 ). The digital terminal  94  displays the transmitted SMS data on the display unit.  
           [0018]    As described above, the related art SMS switching PBX and methods have various disadvantages. For example, in the related art SMS switching private branch exchange, each port of the analog office line interface unit, the ISDN office line interface unit, and the SLT extension line interface unit has to be provided with an SMS unit for exclusive use. Thus, the SMS can not be provided through an office line or the SLT extension line to which an SMS unit is not connected for exclusive use.  
           [0019]    The above references are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.  
         SUMMARY OF THE INVENTION  
         [0020]    An object of the invention is to solve at least the above problems and/or disadvantages and to provide at least the advantages described hereinafter.  
           [0021]    One embodiment of the present invention provides an SMS switching private branch exchange system and method that can efficiently switch SMS without being provided with an SMS unit for exclusive use at an office line interface unit of a private branch exchange or at an SLT extension line interface unit. Another embodiment of the present invention provides an SMS switching private branch exchange system and method that can simultaneously realize functions of SMS signal detection, SMS signal generation, and voice mail service in one board with one chip set, in which a digital signal processor DSP used for voice compression decodes an SMS signal of a PCM format in a voice mail interface unit of a private branch exchange and generates a signal of a PCM format.  
           [0022]    Another embodiment of the present invention provides an SMS switching private branch exchange system that can share a DSP for wholly performing functions of SMS signal detection, SMS signal generation, and voice mail service as a system resource. Another embodiment provides a method for accomplishing the same.  
           [0023]    Another embodiment provides an SMS switching private branch exchange system that can include an office line interface unit which interfaces with an office line; a voice mail interface unit which converts a PCM format SMS signal transmitted from the office line interface unit into SMS data, and converting a format of the SMS data corresponding to a kind of a terminal that will receive SMS; a control unit which switches a PCM channel of an office line to which a speech path is connected into a PCM channel of a usable DSP, and certifying a kind of a terminal which will receive SMS; and an extension line interface unit which transmits an SMS signal having a format corresponding to a kind of the terminal certified by the control unit.  
           [0024]    Another embodiment provides a method for switching SMS of a private branch exchange system that can include certifying whether a usable DSP exists or not when an office line and a speech path are connected to each other; transmitting an SMS signal transmitted from the office line to the DSP if the usable DSP exists; certifying an extension line terminal which will receive the SMS signal; and transmitting the SMS signal to the certified extension line terminal from the DSP.  
           [0025]    Another embodiment provides a method for switching SMS of a private branch exchange system that can include switching a PCM channel of an office line interface unit into a PCM channel of a usable DSP if a speech path is connected to the office line interface unit; transmitting an SMS signal to the DSP from the office line interface unit through the PCM channels; decoding the SMS signal transmitted to the DSP; switching the PCM channel of the DSP into a PCM channel of an SLT extension line interface unit if an extension line terminal which will receive the SMS signal is an SLT; and switching an SMS data channel of the DSP into an SMS data channel of a digital terminal extension line interface unit if an extension line terminal which will receive the SMS signal is a digital terminal.  
           [0026]    Another embodiment provides a private branch exchange system that can include a single digital signal processor that receives a short message service signal in a first format and converts the short message service signal in to a second format and a controller that controls the digital signal processor and determines the second format.  
           [0027]    Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0028]    The invention will be described in detail with reference to the following drawings in which like reference numerals refer to like elements wherein:  
         [0029]    [0029]FIG. 1 is a diagram showing a related art digital private branch exchange for exchanging SMS;  
         [0030]    [0030]FIG. 2 shows a related art method for switching SMS in a digital private branch exchange;  
         [0031]    [0031]FIG. 3 is a diagram showing an SMS switching private branch exchange system according to a preferred embodiment of the present invention; and  
         [0032]    [0032]FIGS. 4A and 4B are flowcharts that show a method for switching SMS in a private branch exchange system according to a preferred embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0033]    [0033]FIG. 3 is a diagram showing construction of an SMS switching private branch exchange system according to a preferred embodiment of the present invention. As shown in FIG. 3, an SMS switching private branch exchange system can convert an SMS signal received through an office line such as a public switched telephone network (PSTN), an ISDN, etc. into a format corresponding to an extension line terminal by using a shared DSP (e.g., shared by time division), and then switches to the corresponding extension line terminal.  
         [0034]    As shown in FIG. 3, an extension line terminal  200  can includes a SLT for SMS  210 ; and a digital terminal  220 . A private branch exchange system  100  can include: an analog office line interface unit  110 ; an ISDN office line interface unit  120 ; a voice mail interface unit  130 ; an SLT extension line interface unit  150 ; a digital terminal extension line interface unit  160 ; and a main processor  140 .  
         [0035]    The analog office line interface unit  110 , the ISDN office line interface unit  120 , the voice mail interface unit  130 , the SLT extension line interface unit  150 , and the main processor  140  are preferably coupled to one another by a PCM bus  170 . Also, the voice mail interface unit  130 , the digital terminal extension line interface unit  160 , and the main processor  140  are preferably coupled to one another by an SMS data bus  180 . The analog office line interface unit  110  interfaces with an analog office line such as a PSTN, etc. The analog office line interface unit  110  can include a CODEC  111  for performing a conversion between an SMS signal of a frequency shift keying (FSK) format and an SMS signal of a PCM format.  
         [0036]    The ISDN office line interface unit  120  interfaces with an ISDN office line. The ISDN office line interface unit  120  transmits/receives an SMS signal of a PCM format between an ISDN office line and the PCM bus  170  preferably by a control of the main processor  140 . The voice mail interface unit  130  can perform functions of SMS signal decoding, SMS signal generation, and voice mail service. The voice mail interface unit  130  can include a digital signal processor (DSP)  131  for compressing voice, reproducing the compressed voice, converting an SMS signal of a PCM format into SMS data, and generating an SMS signal of a PCM format from SMS data; and a memory  132  for storing the compressed voice and decoded SMS data. The main processor  140  can control the entire private branch exchange system  100 , and switch an SMS signal of a PCM format and SMS data according to an extension line terminal.  
         [0037]    The SLT extension line interface unit  150  couples an SLT  210  and the private branch exchange system  100 . The SLT extension line interface unit  150  can include a CODEC  151  for performing a conversion between the switched SMS signal of a PCM format and an SMS signal of an FSK format received from an SLT  210 . The digital terminal extension line interface unit  160  couples the private branch exchange system  100  and the digital terminal  220 .  
         [0038]    Operations of the private branch exchange system according to an embodiment of the present invention will now be described. If a speech path for SMS is coupled through a specific office line, the private branch exchange system  100  certifies whether a usable conversion unit such as DSP  131  exists or not. If the usable DSP  131  exists, an SMS signal is received from a corresponding office line and the received SMS signal is converted into SMS data through the DSP  131 . The private branch exchange system  100  preferably converts a format of the SMS data according an extension line terminal that will receive the SMS data, and switches to a corresponding extension line terminal.  
         [0039]    [0039]FIGS. 4A and 4B show a method for switching SMS in a private branch exchange system according to a preferred embodiment of the present invention. The method shown in FIGS.  4 A- 4 B will be exemplarily described using the PBX  200 . However, the present invention is not intended to be so limited. As shown in FIGS. 4A and 4B, if a speech path for SMS is coupled through a specific office line before receiving an SMS signal (S  00 ), the main processor  140  of the private branch exchange system  100  certifies whether the usable DSP  131  exists in the voice mail interface unit  130  (S 102 ).  
         [0040]    If the usable DSP  131  does not exist at present, the main processor  140  waits for a period of time and then certifies again whether the usable DSP  131  exists or not (S 104 ). If the usable DSP  131  exists, the main processor  140  can switch a PCM channel of an office line to which the speech path is coupled into a PCM channel of the DSP  131  (S 106 ). When the office line to which the speech path is coupled is a PSTN office line, the analog office line interface unit  110  of the private branch exchange system  100  converts an SMS signal of an FSK format transmitted through an analog office line into an SMS signal of a PCM format preferably through the CODEC  111 , and carries the converted SMS signal of the PCM format on the PCM bus  170 . When the office line to which the speech path is coupled is an ISDN office line, the IDSN office line interface unit  120  of the private branch exchange system  100  carries an SMS signal of a PCM format transmitted through an IDSN office line on the PCM bus as it is (S 108 ).  
         [0041]    The main processor  140  performs signaling for receiving an SMS signal and then starts to receive an SMS signal (S 110 ). The DSP  131  decodes the SMS signal of the PCM format carried on the PCM bus  170  and converts it to SMS data (S 112 ). The converted SMS data can be stored in the memory  132  of the voice mail interface unit  130  (S 114 ) transmitted or the like.  
         [0042]    The main processor  140  can determine or certify whether an extension line terminal that will receive the SMS data is a digital terminal or an SLT (S 116 ). If the extension line terminal that will receive the SMS data is an SLT  210 , the main processor  140  switches a PCM channel of an extension line that will receive the SMS data into a PCM channel of the DSP  131  (S 118 ). Then, the main processor  140  performs signaling with the SLT  210  that will receive the SMS (S 120 ). If the signaling with the SLT  210  is completed, the DSP  131  converts the SMS data stored in the memory  132  into an SMS signal of a PCM format and then transmits the signal on the PCM bus  170  (S 122 ).  
         [0043]    The SLT extension line interface unit  150  converts the SMS signal carried on the PCM bus  170  into an FSI format preferably through the CODEC  151 , and transmits the converted SMS signal of an FSK format to the SLT  210  (S 124 ). Then, the SLT  210  can preferably display the transmitted SMS signal on a display unit.  
         [0044]    In the step S 16 , if the extension line terminal that will receive the SMS data is the digital terminal  220 , the main processor  140  couples a SMS data channel of an extension line which will receive the SMS data with a SMS data channel of the DSP  131 . The DSP  131  transmits the SMS data stored in the memory  132  on the SMS data bus  180  as it is (S 126 ). Then, the digital terminal extension line interface unit  160  receives the SMS data carried on the SMS data bus  180 , and transmits the received SMS data to the digital terminal  220  (S 128 ). The digital terminal  220  displays the transmitted SMS data on a display unit.  
         [0045]    Although preferred embodiments of systems and methods were described as signals originating from office lines for delivery to extension lines, the present invention is not intended to be so limited. For example, signals can be transmitted from extension lines for delivery to office lines according to preferred embodiments.  
         [0046]    As described above, preferred embodiments of a PBX and methods thereof according to the present invention have various advantages. For example, according to preferred embodiments, a conversion function such as, the DSP, which can also be used for voice compression, decodes an SMS signal of a PCM format and generates SMS data in an SMS signal of a PCM format, so that functions of SMS signal detection, SMS signal generation, and voice mail service may be simultaneously realized preferably in one board with one chip set and the DSP may be shared as a system resource. Also, the SMS can be efficiently switched without providing an SMS unit for exclusive use at the office line interface unit, the IDSN office line interface unit, and the SLT extension line interface unit, respectively.  
         [0047]    The foregoing embodiments and advantages are merely exemplary and are not to be construed as limiting the present invention. The present teaching can be readily applied to other types of apparatuses. The description of the present invention is intended to be illustrative, and not to limit the scope of the claims. Many alternatives, modifications, and variations will be apparent to those skilled in the art. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures.