JPH0314377B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an abort detection method for automatically restoring the line by detecting the end of data transmission in a switched line modem (modulator/demodulator). This invention relates to an improved abort detection method that prevents malfunctions.

In data transmission using a telephone line, the same control procedure as that of a telephone is used.

In such data transmission using a telephone line, as shown in FIG.
via the other party's modem 13 and center (terminal)
14 and performs data transmission using a telephone line. For example, when the terminal 10 side is the calling side and the center 14 is the called side, and automatic reception is performed at the center 14, a telephone set (not shown) on the terminal 10 side is used to communicate with the other party via the switching center 12. The terminal 10 and the center 14 are called, a line is connected, and data is exchanged between the terminal 10 and the center 14.
In this type of data transmission, the line is restored (disconnected) by hooking off the calling party's telephone or by issuing a message indicating that communication has ended; If the switch is not turned off or the communication end output is not issued, the line will remain connected even after data transmission has finished, which not only wastes line usage charges and is not desirable, but also prevents other users from using the line. The disadvantage is that it cannot be done.

For this reason, the modems 11 and 13 are provided with an abort detection function that detects the end of data transmission and disconnects the line.

[Conventional technology]

Conventionally, in order to detect this abort, a method of monitoring the carrier on the line has been used.

FIG. 6 is a block diagram of such a conventional abort detection method, and FIG. 7 is a waveform diagram of its essential parts.

As shown in FIG. 6, the connection point 20 of the line connection recovery relay 24 selectively connects the line and the telephone set 15 or the demodulation side. After calling the side and connecting the line, connect to the demodulation side as shown in the diagram. After the line is connected, the received signal is sent to the demodulator 21 via the contact 20 of the relay 24.
The received data RD is demodulated and passed to the terminal or center.

On the other hand, the received signal is detected by the CD detection section (carrier detection section)
22 is also input. The CD detection unit 22 detects the carrier included in the received signal, outputs a detection signal CD, and passes it to a terminal or center.

Furthermore, the detection signal CD is input to the abort timer 23, and the detection signal CD is on (with carrier).
If it is off (no carrier), counting (timekeeping) is permitted.

Therefore, as shown in FIG. 7, after a certain OFF time Cot has elapsed since the carrier ceased to exist due to the end of data transmission, the detection signal CD turns OFF.
Abort timer 23 is started and Abt is set for a certain period of time.
If the detection signal CD continues to be off during this period, the abort timer 23 turns on the overflow output, stops driving the relay 24, and switches the contact rl to the telephone side to restore the line.

[Problem that the invention seeks to solve]

In the conventional method of starting the abort timer 23 by turning off the detection signal CD, when noise as shown by the dotted line in FIG. 7 appears on the line, the detection signal CD turns on again and the abort timer 23 starts. There was a problem in that the relay 24 was reset and the relay 24 could not be controlled to recover. Lines passing through such exchanges are particularly noisy due to crosstalk, etc., and the conventional method of detecting the energy of a signal to detect the end of data transmission has caused malfunctions due to the noise.

[Means for solving problems]

The present invention provides an abort detection method that can prevent malfunctions due to noise and the like and perform accurate abort detection.

Therefore, in an abort detection method for detecting the end of data transmission and automatically restoring the line connected to the other party, the present invention monitors the change point of the transmitted data, and the change point of the transmitted data occurs for a certain period of time. The end of the transmission is detected by monitoring both the data quality detection signal that detects the data quality of the received signal and the carrier detection signal that detects the carrier of the received signal, and the end of the transmission is detected. Alternatively, upon detection of the end of reception, an abort timer is started, and the line is automatically restored based on the clocked output of the abort timer.

[Effect]

In the present invention, instead of monitoring the energy of the carrier on the line as in the past, the existence of the transmitted data itself is detected by the change point, so even if noise occurs, the data will remain unchanged. There is no risk of malfunctions because the effect on Furthermore, since existing transmission data is monitored, it can be easily and easily implemented.

On the other hand, the received data is susceptible to line noise due to the exchange network, etc., and if a change point is directly detected as in Japanese Patent Application Laid-open No. 55-121773, malfunctions occur.

Therefore, for received data, a data quality detection signal that does not malfunction due to noise or the like is used to prevent malfunctions due to noise.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to Examples.

FIG. 1 is a block diagram of an embodiment for realizing the present invention. In the figure, the same parts as in FIG. 6 are indicated by the same symbols, 27 is a modulator, and the center (or terminal) 28 is a transmission data monitoring unit that modulates the transmission data from SD and transmits it to the line via the relay 20, and a change point detection circuit 28a that detects the change point of the transmission data SD; Timer 28b reset on output
It has the following.

Next, the operation of the embodiment configuration shown in FIG. 1 will be explained using the operation diagram shown in FIG. 2.

As shown in Figure 1, the interface between the center (terminal) and the modem is as specified in CCITTV.24 or V.28 for transmission, including carrier transmission request signal RS, transmission data SD, and carrier transmission in progress. There is a signal CS, carrier detection signal for reception
CD and received data RD are available. In addition, there are a calling signal CI, a connection OK signal ER, and a timing signal for line control.

In the present invention, transmission data that is least affected by line noise is used to detect the end of data transmission.

That is, the transmission data SD is transmitted to the transmission data monitoring section 28.
The change point is monitored by the change point detection circuit 28a. Since the transmission data is normally a combination of "1" and "0", there are changing points of "1" and "0" in the transmission data.

On the other hand, the change point detection output of the change point detection circuit 28a resets the timer 28b. Therefore, if the change point does not exist for a certain period of time Rt, the timer 28b overflows and produces an off output. The fact that this change point does not exist for a certain period of time Rt indicates that all Z or all A (all data is "1" or "0").

When the timer 28b turns off, the abort timer 23 is activated and starts counting. If the timer 28b continues to turn off, that is, if no change point is detected, the abort timer 23 finishes counting Abt for a predetermined period of time, overflows, and turns on.
This causes relay 24 to operate and contact 2
0 to the telephone and restore the line.

Further, when a change point is detected during the counting period Rt of the timer 28b, the timer 28b is reset so that no overflow occurs and the abort timer 23 is not activated. Similarly, when a change point is detected after the abort timer 23 has been activated, the timer 28b is reset and enters the on state (counting state), and the abort timer 23 stops counting and is reset.

In this way, the change point of the transmitted data is fixed for a certain period of time.
If Rt does not exist, it is assumed that the transmission has ended, and by starting an abort timer, it is possible to monitor the transmitted data and perform abort detection.

In the above embodiment, the transmission data monitoring section 2
8 and the abort timer 23 are shown as separate circuits, but they can also be implemented in one piece of hardware using a microprocessor.

Next, abort detection can be performed more accurately and quickly by using monitoring of received data in combination with such monitoring of transmitted data.

FIG. 3 is a block diagram of another embodiment of the present invention, in which the same parts as in FIG. 1 are indicated by the same symbols, and 25 is a data signal quality detection section;
25a is an integrating circuit that monitors the error of the demodulator 21 and outputs a data signal quality detection signal SQD, and 25b is a threshold circuit that monitors the error of the demodulator 21 and outputs the data signal quality detection signal SQD. It slices at a certain threshold and outputs a data signal quality detection signal SQD that is off (degraded) if it is above the threshold and on if it is below the threshold. 26a is
A NAND circuit, 26b is an AND circuit, and 26c is a flip-flop. These constitute the monitoring circuit 26, and when both signals CD and SQD are on,
The flip-flop 26 is operated by the AND circuit 26b.
c is reset by the NAND circuit 26a when both are off.

21a to 21f are internal configurations of the demodulator 21, 21a is an A/D (analog/digital) converter that converts an analog received signal to digital, and 21b is an AGC circuit that performs automatic gain control. 21c is a roll-off filter that performs waveform shaping; 21d is an automatic equalizer that performs automatic equalization; and 21e is a carrier automatic phase control (CAPC) circuit that performs carrier phase compensation. 21f is a determination circuit that determines the output of the CAPC circuit 21e and issues received data RD; 21g is an error circuit;
It calculates the error between the input and output of the judgment circuit 21f and corrects the automatic equalizer 21d and the CAPC circuit 21e.

29 is a hybrid circuit that connects the modulator 27 and demodulator 21 via a line and relay 20; , AND2 is the second
It is an AND gate that selectively inputs the output of the monitoring circuit 26 to the abort timer 23, and an OR gate.
is an or gate, and the first and second AND gates
The logical sum of the outputs of AND1 and AND2 is input to the abort timer 23.

Next, the operation of the embodiment configuration shown in FIG. 3 will be explained with reference to FIG. 4, which is an explanatory diagram of the operation at the time of reception.

After the line is connected, when the contact 20 of the relay 24 is connected as shown in FIG. 4, a received signal arrives from the line and is input to the demodulator 21 and carrier detector 22. In the demodulator 21, the received signal is A/D converted by the A/D converter 21a, the gain is controlled by the AGC circuit 21b to keep the level constant, and the waveform is shaped by the roll-off filter 21c. 2
Enter in 1d. The automatic equalizer 21d performs automatic waveform equalization, the CAPC circuit 21e compensates for carrier phase errors, and the determination circuit 21f converts the signal into received data RD and outputs it. The error circuit 21g calculates the input/output error of the determination circuit 21f, compensates for the characteristics of the automatic equalizer 21d and the CAPC circuit 21e, and also operates the integration circuit 25a.
Integrate the error by .

The output of the integrating circuit 25a is almost zero as long as automatic equalization can be performed satisfactorily, and the threshold circuit 25b outputs the data signal quality detection signal SQD, which is on, and the quality of the data is good. It is. At the same time, the CD detection section 22 performs carrier detection of the received signal, and detects the carrier detection signal.
Emit a CD.

Therefore, during data transmission, that is, while receiving a received signal, the flip-flop 26c is reset by the AND circuit 26b, and therefore the abort timer 23 is not activated. During this time, quality deterioration occurs, and even if the data signal quality detection signal SQD is turned off, the flip-flop 26c remains reset and the abort timer 23 is not activated.

On the other hand, when the data transmission is completed, the carrier detection signal CD is turned off. On the other hand, due to this, the error of the error circuit 21g also increases rapidly, and the integrator circuit 25a
The output of the threshold circuit 25b also increases.
The data signal quality detection signal SQD from is also turned off.

When both detection signals CD and SQD are turned off, the flip-flop 26c is set by the NAND circuit 26a, and the second AND gate is thereby set.
AND2, abort timer 2 via or gate OR
3 is activated and counting is permitted. After the flip-flop 26c is set, the carrier detection signal
Even if the CD is turned on due to noise or the like as shown by the dotted line in Figure 4, the data signal quality detection signal SQD remains off, so the state of the flip-flop 26c remains unchanged, and it is assumed that the carrier is disconnected, and the abort timer 23 starts counting. Continue to do so. and abort timer 23
When an overflow occurs after counting for a predetermined period of time, the relay 24 is activated to connect the contact 20 to the telephone set, thereby restoring the line.

Also, while the abort timer 23 is counting, both detection signals
When both SQD and CD are turned on, it is assumed that data transmission has started, and the AND circuit 26b resets the flip-flop 26c, resets the abort timer 23, and disables counting.

In the above description, each circuit has been described as a discrete circuit, but it is also possible to perform demodulation, SQD detection, CD detection, and abort detection using calculations by a microprocessor.

Such a reception data monitoring function works by turning on the reception abort detection control signal RAC to open the second AND gate AND2, and the first AND gate AND1 also opens the transmission abort detection control signal SAC. If the control signal RAC is turned on, abort detection can be performed from the transmitted and received data, and if the control signal RAC is turned off, the second AND gate AND
2 is closed, abort detection based on received data is prohibited, abort detection is performed only based on transmitted data, control signal RAC is turned on to open the second AND gate AND2, and control signal SAC is turned off to open the first AND gate AND1. By closing , it becomes possible to detect aborts based only on received data. These can be set by the user using the strap line as appropriate depending on the usage status of communication.

Although the present invention has been described above using one embodiment, the present invention can be modified in various ways according to the gist of the present invention, and these are not excluded from the present invention.

〔Effect of the invention〕

As explained above, according to the present invention, the following effects are achieved.

It does not monitor the energy of the carrier, but instead monitors the change points in the transmitted data, so even if noise occurs on the line, the abort timer will not malfunction, and even if the line is in poor condition, it will not cause the abort timer to malfunction. Recovery can be prevented.

Furthermore, since the received data is not directly detected but the data quality detection signal of the received data is monitored, the abort timer will not malfunction even if noise occurs on the line.

By monitoring the transmitted and received data in this manner, abort detection can be performed accurately and quickly.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment for realizing the present invention, FIG. 2 is an explanatory diagram of the operation of the embodiment in FIG. 1, and FIG. 3 is a block diagram of another embodiment for realizing the present invention. Figure 4 is an explanatory diagram of the operation of the embodiment in Figure 3;
Figure 6 is an explanatory diagram of data transmission using telephone lines.
This figure is a block diagram of a conventional abort detection method, and FIG. 7 is an explanatory diagram of the operation of the structure shown in FIG. In the figure, 10, 14...terminal, 11, 13...modem, 12...exchange, 23...abort timer, 24...line connection recovery relay, 27...modulator, 28...transmission data monitoring section.

Claims (1)

[Claims] 1. In an abort detection method for detecting the end of data transmission and automatically restoring a line connected to the other party, a change point in transmitted data is monitored, and a change point in transmitted data occurs for a certain period of time. detects the end of transmission by monitoring both a data quality detection signal that detects the data quality of the received signal and a carrier detection signal that detects the carrier of the received signal, and detects the end of the transmission. Alternatively, an abort detection method comprising: activating an abort timer upon detection of the end of reception, and automatically restoring the line based on the clocked output of the abort timer.