JPS6311824B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field to which the Invention Pertains] The present invention relates to a simultaneous communication system that performs simultaneous communication of telephone calls and data by frequency-dividing an audio frequency band.

[Prior art and its problems]

FIG. 1 is a block diagram showing a general simultaneous communication system, and FIG. 2 is a block diagram showing a conventional example of a simultaneous communication system in which a plurality of controlled stations are connected to one control station. In Fig. 1, 1 is a modem (modem; MDM), 2 is a telephone, 3 is a high frequency filter (HPF), 4 is a low frequency filter (LPF), 5 is a hybrid coil (three-turn transformer), 6 (6 ₁ to 6 ₃ ) are lines.

In other words, as a method of simultaneously communicating calls and data on one line using the voice frequency band, for example, of the voice band 0.3 to 3.4KHz, frequencies less than 2KHz are used for calls, and frequencies above 2KPH are used for data transmission. A method of frequency division and simultaneous communication is known, and this frequency division involves a set of HPF3 and
LPF4 is used. Therefore, the call
Data is exchanged (bidirectionally) via LPF 4, hybrid 5, and line 6.
The signals are mutually (bidirectionally) transmitted via the HPF 3, the hybrid coil 5, and the line 6.
Note that the HPF can be omitted by providing the modem with a frequency selection function using the HPF.

This is a case where one-to-one communication is performed between devices A and B, but as shown in FIG _.
When SB ₂ , SB ₃ , etc. are connected, the control station CT is provided with a plurality of LPFs 4 corresponding to each line 6 ₁ , 6 ₂ , 6 ₃ , etc., and the LPF 4 and the telephone 2 are connected. A multiplexer 7 for selecting a line is provided between the two. Furthermore, Figure 2 is
This is an example in which the HPF is omitted and the function is assigned to the modem. Therefore, as the number of controlled stations increases,
The disadvantage is that the number of filter LPFs and hybrid coils increases, leading to an increase in cost and an increase in housing space.

[Purpose of the invention]

This invention was made in view of the above, and even when a plurality of controlled stations are connected to a centralized monitoring control station, the control station only needs to be provided with one LPF and a hybrid coil. The purpose is to reduce costs and make it more compact.

[Key points of the invention]

The key point is that the LPF and hybrid coil are installed in the control station in common with the controlled stations, and these are connected to individual lines via line switching means, and in order to prevent data loss due to line switching. The data is continuously transmitted multiple times in a predetermined time interval, and when the data match a predetermined number of times, the data is received as correct.

[Embodiments of the invention]

FIG. 3 is a configuration diagram showing an embodiment of this invention.
Figures A and 3B are explanatory diagrams for explaining the operation.

As is clear from FIG. 3, the control station is provided with one LPF 4, and this LPF 4,
It is configured to be connected to each controlled station SB ₁ , SB ₂ , SB ₃ . . . via the hybrid coil 5 and contact 8 ₂ . Note that ₈₁ is a contact point for connecting the hybrid coil 5 and modem 1,
Reference numeral ₈₃ denotes a contact point for directly connecting the controlled station and the control station, and is operated by a predetermined switch not shown. That is, when the switch is not operating, the contacts 8 ₁ to 8 ₃ are in the positions shown, and when the switch is operating, the contacts 8 ₁ and 8 ₂ are closed and the contact 8 ₃ is open. Note that the other details are the same as in FIG. 2.

Therefore, the switch is not operated and contact 8 ₁
~8 When ₃ is not operating, the solid line in Figure 3A
The routes as shown by L ₁ and L ₂ are the lines 6 ₁ , 6
₂ , 6 ₃ ..., but the modem MDM1 is designed not to respond to call signals from the controlled stations SB ₁ , SB ₂ , SB ₃ ..., so the call signals are not transmitted. First, only the data signal is transmitted via contact ₈₃ and MDM1. In addition, the control station
Predetermined devices are connected to the rear of each modem 1 of the CT and the controlled stations SB ₁ , SB ₂ , SB _{3 .} . . , but are omitted here.

On the other hand, when any one switch, for example, the switch corresponding to controlled station SB ₁ , operates, the 3rd B
A route as shown by the solid line L ₁ ' and the dotted line L ₂ ' in the figure is formed. That is, the data signal and speech signal from the controlled station _SB1 are input to the hybrid coil 5 through the contact ₈₂ , where they are branched into a speech signal and a data signal. The call signal is sent to the telephone 2 via the LPF 4, and the data signal is sent to the contact 8 ₁
, respectively, directly to the modem MDM1, thereby allowing simultaneous communication. This is a case where contacts 8 ₁ to 8 ₃ corresponding to the controlled station SB ₁ are selected, but other controlled stations SB ₁ and SB ₂
When the corresponding contacts 8 ₁ to 8 ₃ are selected, simultaneous communication can be performed in the same manner as described above.

By the way, with the configuration as described above, there is a possibility that a momentary disconnection occurs in the line when switching from the contact point 8 ₃ to 8 ₂ , resulting in loss of transmitted data.

FIG. 4 is an explanatory diagram for explaining such a case. In other words, if a momentary interruption occurs in the line due to switching as shown in b of the figure while data as shown in A in the figure is being transmitted, the received data as shown in C in the figure will be missing as shown in the shaded area. become. Therefore, this invention deals with this problem as follows.

FIG. 5 is an explanatory diagram illustrating the data transmission method according to the present invention, and 6A, 6B, and 6C are explanatory diagrams illustrating how received data is lost when switching lines and how to deal with it.

That is, when transmitting data 1, 2, and 3 as shown in FIG. 5A, the same data is transmitted, for example, four times each, as shown in FIG. 5B. As a result, the number of received data is 4 each as shown in Figure C, and these data are used for majority check or for checking that the data is correct if two of the four match. In addition,
The time width of data transmitted at one time is selected to be longer than the instantaneous interruption time. Therefore,
For transmission data as shown in Figure 6A (a), even if a momentary line disconnection occurs between data 1 and 2 as shown in Figure 6A (b), the destroyed block of data 1 and 2 will be Since there is only one each as shown in (c), data transmission can be guaranteed by using the remaining three pieces of data. Similarly, the sixth
Figure B shows a case where only one block of data is lost for data 1, and Figure 6C shows a case where two blocks of data, the second and third blocks, are lost for data 1, but they are transmitted at one time. Since the time width of the data to be transmitted is selected to be longer than the instantaneous interruption time, it is possible to ensure that the data is transmitted correctly in any of the above cases.

〔Effect of the invention〕

As described above, according to the present invention, even when a plurality of controlled stations are connected to one control station, the LPF and the hybrid coil are provided in common to all the controlled stations, Since it is configured so that it can be selected and used by the switching means, it is possible to not only reduce the cost of the control station side equipment, but also
This has the advantage of being compact. Moreover, since the data transmission time width and the number of times of data transmission are devised to deal with instantaneous line interruptions caused by switching, data reliability is guaranteed.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a general simultaneous communication system, Fig. 2 is a block diagram showing a conventional example of a simultaneous communication system in which a plurality of controlled stations are connected to one control station, and Fig. 3 is a block diagram showing the invention. A configuration diagram showing an example of
3A and 3B are explanatory diagrams for explaining the operation of FIG. 3, FIG. 4 is a timing waveform diagram for explaining the operation during switching, and FIG. 5 is an explanatory diagram for explaining the data transmission method according to the present invention. FIGS. 6A, 6B, and 6C are explanatory diagrams for explaining the manner in which received data is lost due to switching. Code explanation, 1...Modulator/demodulator (modem: MDM),
2...Telephone, 3...High-pass filter (HPF), 4
...Low pass filter (LPF), 5...Hybrid coil, 6...Line, 7...Multiplexer, 8
...line changeover switch, CT ...centralized monitoring and control station,
SB ₁ to SB ₃ ...Controlled stations.

Claims (1)

[Claims] 1. Data transmission between a control station and a plurality of controlled stations connected to the control station via individual lines, each of which includes at least a low-pass filter, and a modem with a high-frequency selection function. route and
A simultaneous communication system in which a transformer is provided to branch the data transmission path and the speech path from the line, and a predetermined frequency band is divided between the control station and the controlled station to simultaneously perform speech communication and data transmission. , the control station includes one low-pass filter and a transformer;
At the time of recovery, each controlled station and the control station are directly connected through each line to form a data transmission path, while during operation, one predetermined line is connected to a reduction filter and a modem through the transformer. and a switching means for forming a simultaneous communication path from the direct path to the simultaneous communication path, and at least the data transmission time width is made longer than the time width required for switching from the direct path to the simultaneous communication path, and the data is continuously transmitted a plurality of times. A simultaneous communication method for calls and data, which is characterized by preventing loss of transmitted data.