JP3370686B2 - ISDN terminal equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an IS that is particularly suitable for data transmission by interconnecting with other networks having different transmission speeds.
It relates to a DN terminal device. 2. Description of the Related Art ISDN is designed to be interconnected (interworked) with other digital networks in addition to a normal telephone network as needed. As a result, ISDN
Terminal device can communicate with terminal devices on other networks. [0003] The transmission speed in the basic service of ISDN is 64 kbps. On the other hand, in other digital circuit networks, besides 64 kbps, for example, there is a 56 kbps in the United States. When the ISDN is interconnected with, for example, a 56 kbps network and communicates between the respective terminal devices,
The terminal device on the ISDN side is, for example, recommended in CCITT Recommendation I. In accordance with H.463 (V.110), it is necessary to perform transmission and reception data speed matching processing. [0005] Here, for example, the terminal device of ISDN is
Consider a case where a call is received from a terminal on another network having a different transmission speed. In this case, the ISDN determines the transmission speed of the interconnected network and sends a call setup message "SE" to the destination terminal.
When sending out a call by sending "TUP", the transmission rate of the network of the calling terminal may be set in the message. This allows
The destination terminal can perform predetermined communication by executing a transmission / reception operation according to the transmission speed. In the ISDN, exchange of control information between networks and stations is performed according to CCITT NO. 7 common line signal system. [0008] Therefore, in order for ISDN to determine the transmission speed of an interconnected network, the network and the NO. It is necessary to exchange control information using a 7-common-line signaling method. However, at present, international IDSNs
In the interconnection of NO. In many cases, the 7 common line signaling method is not adopted. For this reason, in many cases ISD
N cannot receive control information from the interconnected networks and cannot notify the destination terminal of the transmission speed of the calling terminal. In this case, the destination terminal cannot determine the operation state of the transmission speed, and thus starts the communication operation at the standard 64 kbps. That is, when the call setting is completed and the communication link of the B channel is formed, the transmission of the flag signal of the HDLC frame is started. However, at this time, since the predetermined speed matching process has not been performed, the calling terminal cannot detect the flag signal. For this reason, neither the calling terminal nor the called terminal can execute the predetermined transmission control procedure, and has stopped the communication operation as a communication error. Next, consider a case where an ISDN terminal device calls a terminal device of another network having a different transmission speed. In this case, it is necessary for the originating terminal to perform the speed matching process according to the transmission speed of the destination terminal. Therefore, it is necessary for the operator of the calling terminal to perform a setting operation for speed matching processing on the device at the time of calling. However, the operator does not know that such a setting operation is necessary, and makes an outgoing call as it is, or does not know the transmission speed of the destination terminal, so that the setting cannot be made. When the call operation is performed as it is, the terminal device:
The communication operation is started at 64 kbps as described above. That is, when the call setting is completed and the communication link of the B channel is formed, the detection operation of the flag signal of the HDLC frame is started. However, since the predetermined speed matching process has not been performed at this time, the flag signal cannot be detected. Therefore, a communication error occurs as in the above case, and the communication is stopped. If the transmission rate cannot be set, the call cannot be transmitted. [0016] As described above, conventionally,
When the ISDN is interconnected with networks having different transmission speeds, there has been a problem that predetermined communication cannot often be executed between terminals. An object of the present invention is to solve the above problems and to provide an ISDN terminal device capable of reliably communicating even when interconnected with networks having different transmission speeds. For this reason, according to the present invention, when a call is received, after the call connection is completed, one transmission rate is set, and a flag signal of an HDLC frame is transmitted and transmitted. The SABM frame signal from the terminal is detected, and the SAB
If the M frame signal is not detected, the transmission rate is switched to another transmission rate by changing the number of effective bits in one octet of data to be transmitted / received, the HDLC frame flag signal is transmitted to the calling terminal, and the SABM frame signal from the calling terminal is transmitted. Is detected, and when the SABM frame signal is detected, the transmission procedure is executed at the other transmission speed. In the case of the originating terminal, transmission / reception is performed on condition that the flag signal of the HDLC frame is not detected, and in the case of the destination terminal, transmission / reception is performed on condition that the SABM frame signal is not detected. Since the transmission procedure is executed by changing to another transmission rate by changing the number of effective bits in one octet of data, data signals can be transmitted and received even if the transmission rate of the network to which the destination terminal is connected is different. . This allows reliable communication even when interconnected with networks with different transmission speeds. Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a block diagram showing a facsimile apparatus according to a first embodiment of the present invention. In FIG. 1, a facsimile image processing unit 1 performs data compression of image information obtained by reading a document image, or restores received image information and records it on recording paper. The B-channel communication control unit 2 transmits and receives image information by executing a predetermined G4 facsimile transmission control procedure on the B channel. The transmission speed switching section 3 is composed of a 64k / 56k speed matching circuit 31 and a switching circuit 32, and switches the transmission speed between 64 kbps and 56 kbps. The D channel call control unit 4 executes a call setting procedure on the D channel. ISDN interface unit 5
Is connected to the ISDN through a network terminator (not shown),
It transmits and receives signals to and from ISDN. The operation display section 6 displays various information such as the operation state of the apparatus while the operator performs various operations. The control unit 7 is a microcomputer that monitors and controls the above units. With the above configuration, next, as shown in FIG.
The facsimile apparatus 201 of the present embodiment is an ISDN 202
Facsimile apparatus 204 via the digital network 203
A description will be given of a case where the communication is performed. At this time, the transmission speed of the user line in the digital network 203 is 56 k
bps, and the ISDN 202 and the digital network 203 It is assumed that they are not interconnected by 7 common line signaling. Assuming that the call is to be transmitted, the operator sets the destination number and activates the call operation of the facsimile device 201, similarly to a normal facsimile device. When the facsimile apparatus is started, as shown in FIG. 3, it sends out a call setting message "SETUP" to make a call. At this time, "64 kbps" is designated by one information element "transmission capability" (process 101). As shown in FIG. 4, upon receiving the call setup message “SETUP”, the ISDN 202 responds with a call setup acceptance message “CALL PROC” and interconnects with the digital network 203. As a result, the digital network 203 sends a predetermined incoming call signal to the facsimile machine 204 to call the facsimile machine 204. The facsimile machine 204 sends out a communication enable signal in response. Upon confirming the response of the facsimile machine 204, the ISDN 202 sends a response message “CONN” to the facsimile machine 201. These call setup messages are transmitted and received on the D channel. When the facsimile apparatus 201 receives the response message "CONN" and completes the call setup (Process 1)
02, Y), the transmission rate switching unit 3 is in the through state, ie, 64
The operation state is set to kbps (step 103). Next, the timer on the control program is started (processing 1
04), the detection operation of the flag signal of the HDLC frame is performed on the B channel for the fixed time Ta (process 105,
From the N of the process 105 to the process 106, and from the N of the process 106 to the process 105). After sending the communication enable signal, the facsimile apparatus 204 starts sending the flag signal of the HDLC frame. In this case, the facsimile machine 204
The signal is transmitted at 6 kbps. The ISDN 202 and the digital network 203
In this case, CCITT recommendation I. 463 (V.110)
, The speed matching process of the data signal is performed. That is, as shown in FIG. 5, a 56 kbps data signal received from the facsimile apparatus 204 is extracted 7 bits at a time, and 1 bit “1” is added to reconstruct 1 octet of data. Then, this data signal is converted to 64 kbp.
The transmission is made to the facsimile apparatus 201 in s. Also, from a 64 kbps data signal received from the facsimile apparatus 201, 7 bits in which valid data is set in one octet are extracted and transmitted to the facsimile apparatus 204 at 56 kbps. Now, the facsimile apparatus 201 is 64 k
Since all bits in one octet of the received data are read in the operation state of bps, the flag signal is not detected. When the flag signal is not detected and the predetermined time Ta has elapsed (Y in process 106), the operation of the 64 / 56k speed matching circuit 31 in the transmission speed switching unit 3 is enabled to switch to the operation state of 56 kbps. (Process 107). Then, the timer is restarted (process 108), and the detection operation of the flag signal is performed for the fixed time Ta in the same manner as described above (process 109, process 110 from N of process 109, process 1 from N of process 110).
09). The facsimile apparatus 201 operates at 56 kbps.
In the operation state, 7 bits in which valid data is set are read from one octet of the received data. Thus, the flag signal transmitted from the facsimile machine 204 can be detected. When the facsimile apparatus 201 detects the flag signal (Y in step 109), it sends out a SABM frame. This frame is transmitted to the facsimile machine 204, and the facsimile machine 204
Send out the frame. This frame is transmitted to the facsimile machine 201 side, and the facsimile machines 201 and 20
4, a predetermined transmission control procedure is executed. Thus, the image information is transmitted (process 111). If the flag signal is not detected even after switching to the operation state of 56 kbps (Y in step 110), a message indicating a communication error is displayed (step 11).
2) Cancel communication. On the other hand, if the facsimile machine 204 cannot communicate and the call connection is not executed (step 10
2) N), the transmission operation is stopped. Further, when the ISDN 202 is not interconnected with another digital network, or when the interconnected digital network is 64 kbps, the flag signal is detected in the operating state of 64 kbps. In this case, (Process 1
05, Y), the image information is immediately transmitted according to the predetermined transmission control procedure (to step 111). Next, the case where the facsimile apparatus 201 receives a call will be described. When making a call, the facsimile apparatus 204 sends out a predetermined call signal, as shown in FIG. Upon receiving the call signal, the digital network 203
Notify the N202 side. Thereby, the ISDN 202
Sends a call setup message “SE” to the facsimile
TUP "is transmitted. Note that the ISDN 202 and the digital network 203 are now NO. 7 are not interconnected by common line signaling, so ISDN 202
The actual transmission speed on the 03 side cannot be determined. Therefore, "64 kbps" is set in the "transmission capability" of the message. As shown in FIG. 7, when the facsimile apparatus 201 receives a call setup message "SETUP" and receives a call (process 301), it executes a call connection procedure. That is, first, a response message “CONN” is transmitted. IS
Upon receiving this message, the DN 202 responds with a response confirmation message “CONN ACK”. Further, the digital network 203 responds to the facsimile apparatus 204 with a communication enable signal (the above processing 302). Thereafter, the facsimile apparatus 201 checks the content of one information element “transmission capability” of the call setup message “SETUP” (process 303). here,
When the "transmission capability" is "64 kbps"("64k" in step 303), the transmission rate switching unit 3 sets the operation state to 64 kbps (step 304). Then, transmission of the flag signal of the HDLC frame on the B channel is started (process 305). Next, a timer is started (process 3).
06), monitor the reception of the SABM frame for a period of the fixed time Tb (processing 307, processing 307 to processing 30)
8. From N in the process 308 to the process 307). In this case, the ISDN 202 and the digital network 2
03, the speed matching process is executed in the same manner as described above.
At this time, the facsimile apparatus 201 transmits the HDLC frame with all the bits of one octet valid as usual, so that the facsimile apparatus 204 cannot detect the flag signal. Therefore, the facsimile machine 204
Do not send BM frames. When the facsimile apparatus 201 does not receive the SABM frame even after the predetermined time has elapsed (Y in step 308), the facsimile apparatus 201 switches to the operation state of 56 kbps (step 309). Then, the timer is started again (process 310), and the reception of the SABM frame is monitored for a certain period of time Tb (from process 311, N of process 311 to process 312, from N of process 312 to process 311). The facsimile apparatus 201 operates at 56 kbps.
In the operating state of 7 octets, 7 octets
Since the valid data of the bit is set and transmitted, the facsimile apparatus 204 can correctly receive the HDLC frame. Thereby, the facsimile apparatus 204 receives the flag signal and sends out the SABM frame. When the facsimile apparatus 201 receives the SABM frame (Y in step 311), it sends out a UA frame and executes a predetermined transmission control procedure. This allows
Image information is transmitted (process 313). If the SABM frame is not received even after switching to the 56 kbps operation state (N in step 312), a message indicating a communication error is displayed (step 314) and the communication is stopped. On the other hand, when the ISDN 202 is not interconnected with another digital network, or when the digital network to be interconnected is 64
If it is kbps, the SABM frame is received in the operating state of 64 kbps. In this case (Y in step 307), the image information is immediately transmitted according to a predetermined transmission control procedure (to step 313). Further, the ISDN 202 and the digital network 20
3 is NO. When the connection is established by the 7 common channel signaling method, the ISDN 202 is notified that the transmission speed on the digital network 203 side is 56 kbps. In this case, I
The SDN 202 specifies “56 kbps” in the “transmission capacity” of the call setup message “SETUP”. When the facsimile apparatus 201 specifies "56 kbps" in the "transmission capability"("56k" in the process 303), the facsimile apparatus 201 immediately transmits the 56 kbps.
(Step 30)
9). As described above, in this embodiment, when a call is connected to a destination terminal by making and receiving a call, the transmission speed is first set to 64 k.
bps, the detection and transmission of the flag signal or the reception of a predetermined frame is monitored. If the predetermined operation is not performed, the transmission speed is switched to 56 kbps, and the same operation is performed again. I have. As a result, even when the transmission speed of the digital network interconnected by the ISDN network or the destination terminal device is 56 kbps, no communication error occurs as in the related art.
Communication is assured. In the above-described embodiment, an example in which the transmission rate is switched from the standard 64 kbps to another one 56 kbps has been described. You may. Further, it is natural that the transmission speed to be switched may be set arbitrarily according to the other terminal. Although the case of interconnecting with another digital network has been described, it goes without saying that the same applies to the case of interconnecting with another ISDN network having a different transmission speed. In the transmission procedure of the above-described embodiment, the destination terminal sends the flag signal first, but the calling terminal may send the flag signal first. In this case, ISD
The terminal N may detect the flag signal at the time of incoming call in the same manner as at the time of calling. Further, a facsimile apparatus has been described as an example of an ISDN terminal. However, it goes without saying that the present invention can be similarly applied to various ISDN data terminal apparatuses. As described above, according to the present invention, on the condition that the flag signal of the HDLC frame is not detected in the case of the originating terminal, the SABM frame signal is generated in the case of the destination terminal. The transmission procedure is executed by changing the number of effective bits in one octet of data to be transmitted and received on the condition that the transmission is not detected, so that the transmission procedure is executed. Also enables transmission and reception of data signals. This allows reliable communication even when interconnected with networks with different transmission speeds.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a facsimile apparatus according to an embodiment of the present invention. FIG. 2 is an explanatory diagram showing an example of a communication mode. FIG. 3 is an operation flowchart of the facsimile apparatus at the time of transmission. FIG. 4 is an explanatory diagram showing a transmission control procedure at the time of transmission by the facsimile apparatus. FIG. 5 is an explanatory diagram showing a transmission speed matching process. FIG. 6 is an explanatory diagram of a transmission control procedure when the facsimile apparatus receives a call. FIG. 7 is an operation flowchart when the facsimile apparatus receives a call; [Description of Signs] 1 facsimile image processing unit 2 B channel communication control unit 3 transmission speed switching unit 4 D channel call control unit 5 ISDN interface unit 5 6 operation display unit 7 control unit 31 64k / 56k speed matching circuit 32 switching circuit 201 , 204 Facsimile machine 202 ISDN 203, 203 Digital network

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04N 1/32-1/34 H04M 11/00-11/10 H04L 29/00-29/12

Claims (1)

(57) Claims 1. An ISDN for interconnecting with another network having a different transmission rate and transmitting data between terminals connected to each network.
In the terminal device, after receiving the call and completing the call connection, set one transmission speed and
A signal transmission detecting means for transmitting a flag signal of the LC frame to the calling terminal and detecting a SABM frame signal from the calling terminal; and when the SABM frame signal is not detected within a predetermined time, one octet of data to be transmitted and received. Signal transmission detection and re-execution means for re-executing transmission of the flag signal of the HDLC frame and detection of the SABM frame signal by switching to another transmission rate by changing the number of effective bits, and detecting the SABM frame signal Transmission means for transmitting a UA frame signal at another transmission speed to execute data transmission.