JP2619664B2 - Off-hook detection method for telephone accessory - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a method for detecting off-hook of a telephone accessory, and more particularly to a method for detecting an idle state of a telephone line when dialing out a data communication device attached to the telephone. The present invention relates to a method for detecting off-hook of a telephone accessory.

(Prior art) In recent years, with the diversification and sophistication of user needs, a large-capacity database or a central host computer has been connected to a high-performance terminal via a network, and railway tickets, air tickets, and the like have been connected. 2. Description of the Related Art Data communication services for ticketing, patent or technical information retrieval, newspaper article information retrieval, provision of product information and sightseeing information, sales inventory management, and the like have become widespread.

Large-scale data communication services that constantly handle large amounts of data use dedicated lines and terminals with advanced functions, while small-scale data communication services use a public telephone line, which is a subscribed telephone network. A variety of services can be enjoyed with a telephone set having a data communication function.

When a data communication device with an automatic dialing function is connected to a telephone line whose primary purpose is to use the telephone, make sure that the data communication device does not start dialing while using the telephone and interrupts the call. It is necessary to take measures.

For this reason, this type of data communication device generally has an off-hook detection circuit for detecting whether the handset is on the telephone, that is, whether or not the telephone is busy, is interposed in series between the telephone and the telephone line. Have been.

This off-hook detection is realized by determining whether or not the telephone is in use based on the presence or absence of a call current flowing through a normal telephone line.

That is, a current detecting element such as a photocoupler is inserted in series on one side of a pair of telephone lines, and based on a detection signal from the detecting element, for example, if a call signal is output, during that time, the data communication device The dialing is prohibited to prevent interference.

In such a conventional off-hook detection method, since a part of the current detection element is inserted in series in the telephone line itself, the call current can be accurately detected.
If the current detection element breaks down for some reason,
At the same time, the telephone line is disconnected, which causes a problem that not only the data communication device but also the telephone cannot be used.

For this reason, especially when high reliability is required, for example, when a third party installs a data communication device to provide additional services to the telephone user,
Since the non-conductive destruction of the current detecting element such as a photocoupler has a great effect, a relay winding or the like having a large allowance for a large current is used as the current detecting element.

However, when a relay winding is used, the relay winding is connected in series to one of the pair of telephone lines, so that when using the telephone, a small amount of noise is mixed into the telephone line, and the voice quality during a call is reduced. However, there was a problem that the deterioration was not small. It is considered that this noise is caused by an unnecessary voltage generated in the coil due to a magnetic field around the coil.

(Object of the Invention) The object of the present invention is to solve the above-mentioned problems of the prior art,
An object of the present invention is to provide a method of detecting off-hook of a telephone accessory, which can minimize noise mixing into a call current through a relay winding unit.

In order to achieve the above object, the off-hook detection method for a telephone accessory according to the present invention comprises the steps of: In the off-hook detection method of a telephone accessory which detects whether the data communication device is activated or not, the relay winding is normally short-circuited by a bypass switch to bypass the relay winding to the telephone. Opening a bypass switch to detect the telephone line is idle (whether a call is being made) only immediately before the data communication device starts dialing, and to prevent the noise from entering the relay Detecting the call current by conducting the line section, and switching the telephone line to the data transmission / reception section when the call current is not detected It is characterized.

(Embodiment) Hereinafter, a method for detecting off-hook of a telephone accessory according to the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a block circuit diagram to which the method of the present invention is applied. A data communication device 3 is interposed between a telephone 1 and a pair of telephone lines 2. The data communication device 3 includes an off-hook detection circuit 4 for detecting an idle state of a telephone line,
A data transmission / reception unit 5 for realizing an information transmission operation with a host computer (not shown) and a telephone line 1 and a data transmission / reception unit 5 are inserted in series with each telephone line in order to selectively switch the data transmission / reception unit 5. It is composed of relay contacts 6 and 7.

The off-hook detection circuit 4 includes a relay winding unit 8 connected in series to one side of the telephone line 2, a bypass capacitor 9 connected in parallel to the relay winding unit 8, and a relay winding unit 8.
And a switch 10 connected in parallel to the bypass capacitor 9. The bypass capacitor 9 bypasses the audio signal so as not to be attenuated by the relay winding unit 8. The switch 10 bypasses the relay winding unit 8 by closing during use of the telephone, and opens for a short time to detect the use of the telephone before starting dialing. It is a part that fulfills the characteristic function in.

The data transmitting / receiving unit 5 is provided with a relay contact 11 that closes when a talk current is detected in the relay winding unit 8.

The gist of the method of the present invention is that a bypass path including another switch 10 is formed in the off-hook detection circuit 4 so that a communication current when a normal telephone is used flows through the bypass path and is connected in series to a telephone line. By connecting to the relay winding section 8 only at the time of detecting the talk current, it is possible to minimize the entry of noise into the talk current due to the relay winding.

 The operation of the method of the present invention in the above configuration will be described.

The connection switching between the telephone 1 and the data transmission / reception unit 5 is performed by relay contacts 6 and 7 provided inside the data communication device 3 and provided in series with each of a pair of telephone lines. Is in the solid line position as shown in the figure, the telephone 1 and the telephone line 2 are connected, and the telephone becomes communicable.

On the other hand, when the relay contacts 6 and 7 are switched to the dotted line positions,
The telephone 1 is disconnected, and the telephone line and the data transmission / reception unit 5 are connected, so that data communication using the telephone line becomes possible.

Note that the switch 10 is used as in the conventional off-hook detection circuit.
Is not provided, when the relay contacts 6 and 7 are connected to the solid line side and the telephone is off-hook, a call current flows, and the relay winding part 8 inserted in series to one of the telephone lines 2 As described above, there is a problem that noise generated by the above is mixed.

In order to solve such a problem, in the method of the present invention, a switch 10 for forming a call current bypass path in parallel with the relay winding section 8 is newly provided. The communication path is prevented from conducting and the bypass path is used as a communication current path.

That is, in FIG. 1, when the relay contacts 6 and 7 are switched to the dotted line side and the data transmitting / receiving unit 5 starts data communication, it is determined whether or not there is a call current before starting. At this time, the switch 10 is first opened to make the bypass path DC non-conductive, and at the same time, the relay winding part 8 is made conductive to open and close the relay contact 11 provided in the data transmitting and receiving part 5. Detects the presence or absence of call current.

That is, when it is determined that the relay contact 11 is closed and a call current is flowing, since the telephone is in use, the switch 10 is immediately closed to make the bypass path conductive again to connect to the winding 8. Prohibiting the conduction of the call current can effectively prevent noise from entering the telephone line.

Next, when it is determined that the telephone is not used due to the opening of the relay contact 11, the relay contacts 6, 7 are switched to the dotted lines to connect the data transmitting / receiving unit 5 to the telephone line 2 to perform predetermined information communication. After the operation, the relay contacts 6, 7 are returned to the solid line side. During this time, the telephone 1 is disconnected from the telephone line 2.

According to the method of the present invention, since a third party provides another data communication service to a telephone user, the reliability of the apparatus is improved, for example, when a data communication apparatus is installed in common with the telephone line of the telephone. be able to.

(Effects of the Invention) As described above, according to the off-hook detection method of the telephone accessory according to the present invention, the off-hook detection circuit of the telephone is configured by a switch connected in parallel with the relay winding of the off-hook detection circuit. By flowing the current through the bypass path, it is possible to minimize noise mixing in the talk current by the relay winding.

[Brief description of the drawings]

FIG. 1 is a block circuit diagram to which the method of the present invention is applied. DESCRIPTION OF SYMBOLS 1 ... Telephone, 2 ... Telephone line 3 ... Data communication device, 4 ... Off-hook detection circuit, 5
… Data transmission / reception unit 6, 7… Relay contact, 8… Relay winding unit 9… Bypass capacitor, 10… Switch

Claims (1)

(57) [Claims] 1. A data communication apparatus which shares a pair of telephone lines with a telephone before starting automatic dialing by detecting the presence or absence of a telephone call current through a relay winding connected in series to one of the telephone lines. In a method of detecting off-hook of a telephone accessory that determines whether or not to operate a communication device, a bypass switch is provided in parallel with the relay winding unit, and during a normal telephone call, the bypass switch is closed and a call current is supplied to the bypass switch. A telephone that detects the presence or absence of a call current by opening the bypass switch and making the relay winding portion drivable only immediately before the automatic dial transmission of the data communication device starts. Off-hook detection method for attached equipment.