JPH0343836B2 - - Google Patents

Description

[Detailed Description of the Invention] [Summary] A device that receives digital signals including clock signals, data signals, and call control signals and transmits them to subsequent devices, which temporarily holds a predetermined amount of the received digital signals. When a digital signal interruption is detected, a retained digital signal is transmitted to a subsequent device instead of a received digital signal, thereby preventing abnormal call disconnection.

[Industrial application field]

The present invention provides a signal disconnection processing method that makes it possible to prevent abnormal call disconnections when digital signals are interrupted in a device that receives digital signals including clock signals, data signals, and call control signals and transmits them to downstream devices. Regarding.

[Conventional technology]

In a digital exchange, etc., a digital terminal that accommodates digital transmission lines, a line concentrator that accommodates subscriber lines, an analog trunk that accommodates analog transmission lines, and various signal tones are supplied to the communication line network that connects each call. A signal tone generating device and the like are connected to each terminal, and each transmits and receives digital signals to and from the communication channel network via the highway.

FIG. 3 is a diagram showing an example of a signal transmission path to which the present invention is applied, FIG. 4 is a diagram showing an example of the signal format in FIG. 3, and FIG. It is a figure showing an example.

In FIG. 3, a communication network 1 and a digital terminal 2 are connected by highways 3 and 4. In FIG.

As shown in Fig. 4, the signal format of the digital signals transmitted by each highway 3 and 4 is such that 32 time slots TS are provided in a frame F that is repeatedly transmitted at predetermined intervals.
0, the clock signal, time slot TS16, the call control signal, time slot TS1 to TS1.
5 and time slots TS17 to TS31, the data signals for 30 communication paths are sent to CMI.
(Coded Mark Inversion) format.

In the digital terminal 2, a code conversion circuit 5 extracts clock signals from the various signals arriving from the highway 3 and transmits them to a clock generation circuit 6, and converts call control signals and data signals from CMI format to NRZ (Non Return). to Zero)
After converting it into a format, it is transmitted to the memory control circuit 7.

The clock generation circuit 6 has a built-in clock oscillator and controls the clock oscillator so as to generate a clock signal synchronized with the clock signal transmitted from the code conversion circuit 5.

Based on the clock signal transmitted from the clock generation circuit 6, the memory control circuit 7 temporarily stores the call control signal and data signal transmitted from the code conversion circuit 5 in a memory 8 for a predetermined amount, and then sequentially extracts the signals. Digital Terminal 2 via Route 9
The information is transmitted to a downstream device (not shown) within the system.

If a fault occurs on the highway 3 and normal signals are no longer transmitted to the digital terminal 2, the code conversion circuit 5 in the digital terminal 2
The clock signal, call control signal, and data signal transmitted to the clock signal are all in an abnormal state, and the code conversion circuit 5 cannot reliably extract the clock signal. It becomes impossible to generate a clock signal synchronized with the signal, and the memory control circuit 7 handles call control signals and data signals that are in an abnormal state.
It is output via memory 8 to signal path 9 .

In particular, when the call control signal becomes abnormal,
For example, a failure occurs such as a call being set up being abnormally disconnected.

[Problem that the invention seeks to solve]

As is clear from the above explanation, in the conventional signal disconnection processing method, when an abnormality occurs on the highway 3 and the digital signal transmitted from the communication path network 1 to the digital terminal 2 becomes abnormal, the digital terminal In No. 2, there was a problem in which failures such as abnormal call disconnections occurred.

[Means for solving problems]

FIG. 1 is a diagram showing the principle of the present invention.

In FIG. 1, 3 is a highway through which digital signals including clock signals, data signals and call control signals are transmitted, and 200 is a clock generating means for generating a clock signal synchronized with the clock signal arriving from the highway 3.

Reference numeral 100 is a signal interruption detection means provided according to the present invention for detecting interruption of the digital signal.

Reference numeral 300 is a data holding means provided according to the present invention, which temporarily holds a predetermined amount of received call control signals and data signals.

Reference numeral 400 is provided according to the present invention, and when the signal interruption detection means 100 detects interruption of the digital signal, it stops transmitting the received call control signal and data signal to the downstream device, and the data holding means 3
This switching means transmits the call control signal and data signal held before the digital signal is interrupted at 00 to the subsequent device.

[Effect]

If the digital signal is normally transmitted from the highway 3 and the signal interruption detection means 100 does not detect any interruption, the call control signal and data signal transmitted from the highway 3 are transmitted to the data holding means 300 and the switching means 400. The data holding means 300 temporarily holds a predetermined amount of the transmitted digital signals, and then sequentially transmits them to the switching means 400.

The switching means 400 selects the call control signal and the data signal transmitted from the highway 3 and transmits them to the subsequent device when the signal interruption detection means 100 does not detect the interruption of the digital signal.

When the signal interruption detection means 100 detects an interruption of the digital signal, the clock generation means 200 outputs an internally generated clock signal.

Furthermore, the switching means 400 stops transmitting the received call control signal and data signal to the subsequent device, and transfers the call control signal and data signal that had been held before the digital signal is interrupted to the data holding means 300 to the subsequent device. Communicate to the device.

Since the call control signal is held in the state it was in before the digital signal was lost, the subsequent device maintains the call setting state in the state it was in before the digital signal was lost, and if the call is abnormal due to the digital signal loss. There is no longer any fear of being cut off.

Note that the data signal also repeats the state before the digital signal was interrupted, but for highly redundant data such as voice, it is very likely that the old data signal will be repeated until the digital signal returns to normal. There is no effect on downstream devices.

As described above, even if the transmission of digital signals is interrupted, there is no possibility that the call will be abnormally disconnected, and the call being set up will be maintained.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is a diagram showing a signal interruption processing method according to an embodiment of the present invention. Note that the same reference numerals indicate the same objects throughout the figures. The target signal transmission path is as shown in FIG. 3, and the signal format is as shown in FIG. 4.

In FIG. 2, a signal disconnection detection circuit 10 is provided as a signal disconnection detection means 100, and a switching section 71 is provided as a switching means 400 in the memory control circuit 7a.

In FIG. 2, the code conversion circuit 5 converts the various signals arriving from the highway 3 in the same manner as described above.
The clock signal is extracted and transmitted to the clock generation circuit 6, and after being converted from the CMI format to the NRZ format, it is transmitted to the memory control circuit 7.

On the other hand, the signal interruption detection circuit 10 does not output the detection signals d1 and d2 when the digital signal transmitted from the highway 3 is not interrupted and is transmitted normally.

As a result, the clock generation circuit 6 generates a clock signal synchronized with the clock signal transmitted from the code conversion circuit 5, as described above, and the memory control circuit 7 generates a clock signal synchronized with the clock signal transmitted from the code conversion circuit 5. After the data signals are temporarily stored in the memory 8, they are sequentially extracted and sent to the downstream device in the digital terminal 2 via the signal path 9.

In this situation, a problem occurred on Highway 3,
When a normal signal is no longer transmitted to the digital terminal 2, the signal interruption detection circuit 10 detects the interruption of the digital signal and transmits detection signals d1 and d2 to the clock generation circuit 6 and the memory control circuit 7a.

Clock generation circuit 6 receiving detection signal d1
stops synchronizing the built-in clock oscillator with the clock signal transmitted from the code conversion circuit 5, and outputs the clock signal generated by the clock oscillator.

On the other hand, the memory control circuit 7 which received the detection signal d2
a activates the switching unit 71.

The switching unit 71 stops storing the abnormal call control signal and data signal transmitted from the code conversion circuit 5 in the memory 8, and stores the normal call control signal and data signal stored in the memory 8 until then. A data signal is repeatedly sent out on signal path 9.

As a result, the call control signal and data signal before the occurrence of the abnormality on the highway 3 are repeatedly sent to the signal path 9.

A subsequent device that receives such a call control signal holds the set call and is prevented from abnormally disconnecting the call.

The digital terminal 2 notifies the communication network 1 of the digital signal interruption detected by the signal interruption detection circuit 10 via the highway 4, for example. The communication channel network 1 switches to, for example, a redundant standby device and processes the normal digital signal so as to transmit it to the digital terminal 2.

As is clear from the above description, according to this embodiment, when a failure occurs on the highway 3 and the digital signal transmitted to the digital terminal 2 is interrupted, the clock generation circuit 6 generates its own clock signal. However, before the digital signal is interrupted, the call control signals and data signals stored in the memory 8 will be sent out repeatedly, and the abnormal call control signals and data signals will not be transmitted to the downstream device. and calls are prevented from being dropped.

Note that FIGS. 2, 3, and 4 are merely examples of the present invention, and for example, the code conversion circuit 5, the clock generation circuit 6, the memory control circuit 7a,
The device equipped with the memory 8 and the signal disconnection detection circuit 10 is not limited to the digital terminal 2, and many other modifications such as a line concentrator, an analog trunk, a signal tone generator, etc. can be considered, but in any case. However, the effect of the present invention remains unchanged.

〔Effect of the invention〕

As described above, according to the present invention, even if the transmission of digital signals is interrupted in the device, there is no possibility that the call will be abnormally disconnected, and the call being set up will be maintained.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the principle of the present invention, FIG. 2 is a diagram showing a signal disconnection processing method according to an embodiment of the present invention, and FIG. 3 is a diagram showing an example of a signal transmission path to which the present invention is applied. FIG. 4 is a diagram showing an example of the signal format in FIG. 3, and FIG. 5 is a diagram showing an example of a conventional signal disconnection processing method. In the figure, 1 is a communication path network, 2 is a digital terminal, 3 and 4 are highways, 5 is a code conversion circuit, 6 is a clock generation circuit, 7 and 7a are memory control circuits, 8 is a memory, 9 is a signal path, and 10
71 is a switching section; 100 is a signal interruption detection means; 200 is a clock generation means; 300 is a signal interruption detection circuit;
4 indicates a data holding means, and 400 indicates a switching means.

Claims (1)

[Claims] 1. The clock generating means 200 receives a digital signal including a clock signal, a call control signal, and a data signal, and generates a clock signal synchronized with the clock signal.
A device for transmitting the call control signal and the data signal to a downstream device, the device comprising: a signal interruption detection means 100 for detecting the interruption of the digital signal; Data holding means 300
and, when the signal interruption detection means 100 detects the interruption of the digital signal, it stops transmitting the received call control signal and data signal to the downstream device, and stores the digital signal in the data holding means 300. and switching means 400 for transmitting the call control signal and data signal held before the signal is interrupted to the downstream device, and when the signal interruption detection means 100 detects the interruption of the digital signal, A signal interruption processing method characterized in that the clock generating means 200 is made to stop synchronizing with the clock signal included in the digital signal.