JPH044654A - Communication method between center equipment and terminal equipment through public telephone network - Google Patents

Abstract

PURPOSE:To prevent collision between a reply signal sent from a terminal equipment and an identification number sent from a center equipment by using combination of plural signals whose transmission levels are different as the identification signal representing a connection request from the center equipment to a data terminal equipment. CONSTITUTION:Signals of a comparatively small level are used for identification signals 1, 3 and a signal of a usual transmission level is used for an identification signal 2. The changeover of the transmission level is implemented by an attenuator 23. The reason why the identification signals 1, 3 are used is to estimate whether or not the identification signal is received by a terminal equipment and the identification signal 2 is used as a connection request signal to a data terminal equipment aiming at the reception. The center equipment 1 monitors the identification signals 1-3 and when the identification signal is correctly monitored, it is estimated that the terminal equipment receives the identification signal 2 and succeeding connection procedure is executed.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a communication method between a center device and a terminal device via a public telephone network, and particularly relates to a telephone set and data terminal equipment in which the terminal device switches and shares one line. The present invention relates to a connection method when the device is equipped with the following.

[Conventional technology] The main conventional technology of this type is to automatically call the center from the terminal at a preset time, and in this case, the center cannot activate the terminal. There were drawbacks.

This shortcoming can be resolved and the terminal side can be started from the center side1
One method is to file an earlier application by the applicant (Japanese Patent Application No.
245761).

In this method, the center device sends an identification signal and releases the line if it detects a line polarity reversal within a certain time after sending a selection signal, or releases the line if it does not detect a line polarity reversal for a certain period of time. The terminal device detects off-hook of the telephone after the ringing signal stops or before the ringing signal stops within a certain period of time when the ringing signal does not stop for a certain period of time, and detects the identification signal from the center device. After one line is detected to be open, a call is made to the center equipment and the data terminal equipment is connected to the public telephone network.

[Problems to be Solved by the Invention] In this method, as shown in FIG. 4, when a selection signal for selecting a specific terminal device is sent from the center device, the specific terminal device is selected by the exchange and a bell signal is emitted. It is sent to the terminal side via the network control device.

When an attached device such as a telephone, FAX, or answering machine (hereinafter collectively referred to as a telephone) responds on the terminal side, the loop is closed and the polarity of the line is reversed.

The center device detects this polarity reversal and sends an identification signal indicating a connection request for the data terminal device to the terminal side. In response to this, a response such as voice, fax, or answering machine is sent from the terminal device to the center device. However, in this case, since the center equipment sends out the identification signal immediately after detecting the polarity reversal of the line, the identification signal sent from the center equipment on the terminal side is rejected due to a collision with the response signal transferred from the terminal equipment. It may not be possible to receive it correctly.

The present invention prevents collision between the response signal transmitted from the above-mentioned terminal device and the identification signal transmitted from the center device, and provides a highly reliable public telephone in which connection requests from the center device are correctly transmitted to the terminal device side. The purpose of this invention is to provide a communication method between a center device and a terminal device via a network.

[Means for Solving the Problems] The present invention uses a combination of a plurality of signals having different transmission levels as an identification signal indicating a connection request from a center device to a data terminal device.

[Operation] By performing the communication method between the co-center device and the terminal device as described above, the center device monitors the identification signal sent to the terminal device side, and estimates whether or not this identification signal was correctly received on the terminal device side. be able to. Therefore, the reliability of identification signal communication can be improved, and the above-mentioned problems can be solved.

[Example] An example of the present invention will be described in detail below with reference to the drawings.

FIG. 3 is a block diagram showing the system configuration of a communication device to which the communication method of the present invention is applied. The communication device includes a center device 1, a terminal device 3, and a public telephone network 2 that connects the center device 1 and the terminal device 3. If the polarity of the line is reversed within a certain period of time after sending the selection signal (dial signal), the center equipment N1 will send out an identification signal and open the line. It is equipped with a transmitting section 13 that releases the. Terminal device 3
is a telephone (or an attached device such as a fax machine or an answering machine) 6,
It includes a data terminal device 5 and a network control device 4.

Further, the network control device 4 of the terminal device 3 includes a hook state monitoring circuit 7 for detecting the hook state of the telephone 6, a paging signal detection circuit 8 for detecting a paging signal, and an identification signal detecting circuit for detecting an identification signal from the transmitting unit 13 of the center device 1. A signal detection circuit 9, a current detector 10 that detects the hook state of the telephone 6 and a calling signal, a relay contact 11 that switches between the telephone 6 and the data terminal equipment 5, a hook state monitoring circuit 7, a calling signal detection circuit 8, and an identification signal detection circuit. The control circuit 12 receives a signal from the circuit 9 and controls a relay (not shown) having the relay contact 11.

In order to implement the communication method of the present invention in the communication device shown in FIG. 3, it is necessary to change the configuration of the center device 1 from the conventional configuration.

Figure 5 shows the center installation when using the conventional method! 1, and FIG. 2 shows a partial block diagram when the present invention is adopted.

Furthermore, FIG. 1 is a diagram for explaining the communication method of the present invention, and when compared with the explanatory diagram of the conventional communication method shown in FIG. 4, the procedure up to the detection of polarity reversal on the center device side is the same.

In Fig. 5 and Fig. 2, 51.21 is the center mounting M.
This is an identification signal sending circuit that sends out an identification signal indicating that the communication is from 1. For example, PB)-- is used as the identification signal. Further, 52 and 22 are line control circuits for automatically making calls to public telephone lines, and have the functions of loop closure and selection signal sending. 24 is line control circuit 2
2 to the public telephone line and the line control circuit 2
2 is a hybrid circuit for separating signals received from the public telephone line via 2; 23 is an identification signal sending circuit 21;
An attenuator is used to attenuate the level of the signal sent from the terminal to the public telephone line, and the attenuation amount can be switched and controlled. 25 is a signal receiving circuit that detects signals on the public telephone line and monitors identification signals.

Next, the communication method of the present invention will be explained with reference to FIG. The procedure up to the detection of the polarity inversion signal by the center device 1 is the same as that of the conventional method, as described above. In the present invention, the line signal is detected (A) for a certain period of time (T1) after the polarity inversion signal is detected through the signal receiving circuit 25 shown in FIG. It is desirable to set the line signal detection level at this time to a level that does not detect line noise but only detects the response signal transmitted from the terminal side. However, since it is generally difficult to completely satisfy this condition, the normal detection level is set to a level at which line noise is not detected, that is, about -25 dBm.

In this case, it may not be possible to detect that the response signal is sent from the terminal device 3, but if the communication of the identification signal is reliably performed by the operation detailed below and the detection of the line signal is disconnected (B). , identification signals 1 to 3 (C
-E) and at the same time monitor these identification signals 1 to 3 (
Do F).

A feature of the present invention is that a plurality of signals with different transmission levels are used in combination as an identification signal indicating a connection request to a data terminal device, but in the case of this embodiment, a combination of three signals is used. , identification signals 1 and 3 are relatively low level signals (eg -20 dBm), and identification signal 2 is set to a normal transmission level (eg -8 dBm). This switching of the output level is performed by an attenuator 23 shown in FIG. The purpose of using the identification signal 1.3 is to estimate whether the terminal side can receive the identification signal. Further, the identification signal 2 is used as a connection request signal to a data terminal device for reception on the terminal side. The center device 1 side monitors the identification signals 1 to 3, and when the identification signals can be correctly monitored, the terminal side assumes that the identification signal 2 has been received and executes the subsequent connection procedure.

In this case, if the identification signals 1 to 3 cannot be detected on the center equipment W1 side, the line signal is detected again and the above-described procedure is repeated.

[Effects of the Invention] As explained above, in the conventional communication method, the identification signal and the response signal from the terminal side collide, and when the terminal device side cannot receive the identification signal, the center device receives the response signal from the terminal device side in the subsequent step. However, in the present invention, the center apparatus can estimate the reception result of the identification signal on the terminal apparatus side. Therefore, when the identification signal cannot be received by the terminal device as in the conventional method, there is no need to make a call again from the center side, which not only improves the reliability of identification signal communication but also shortens the communication connection time. This has the advantage of reducing unnecessary telephone charges.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining a communication procedure according to the communication method of the present invention, FIG. 2 is a detailed block diagram of a center device used in the present invention, and FIG. 3 is a schematic configuration of a communication device to which the present invention is applied. FIG. 4 is a diagram for explaining the communication procedure of the conventional system, and FIG. 5 is a block diagram showing the configuration of the center device according to the conventional system. In the figure, A...Line signal detection, B...
- Signal disconnection detection, C...Identification signal 1. D...
...Identification signal 2゜E...Identification signal 3, F...
...Identification signal monitor, 21...Identification signal sending circuit, 22...Line control circuit, 23...
・Attenuator, 24...Hybrid circuit,
25... Signal receiving circuit. Patent applicant: Oki Electric Industry Co., Ltd. Agent: Takashi Kumagai (1 other person)

Claims (3)

[Claims] (1) A terminal device equipped with a telephone and data terminal equipment that can be shared by switching one line, and a center device connected to a center device via a public telephone network to communicate with a center device and a terminal device connected to the public telephone network. Communication method between a center device and a terminal device via a public telephone network, characterized in that a plurality of signals having different transmission levels are used in combination as an identification signal indicating a connection request from the center device to the data terminal device. Method. (2) Claim (1) characterized in that the identification signal is monitored by the center device, and when the identification signal can be correctly monitored, the terminal device side determines that the identification signal has been received and executes a subsequent connection procedure. ) Communication method between the center device and the terminal device using the public telephone network. (3) Among the identification signals, a signal with a low transmission level is used as a monitor for receiving the identification signal on the terminal device side, and a signal with a high transmission level is used as a connection request signal to the data terminal equipment. A communication method between a center device and a terminal device via a public telephone network according to claim (1).