KR0138185B1 - Electronic exchange system - Google Patents

Abstract

[Technical field to which the invention described in the claims belong]

The present invention relates to a method for transmitting a dual tone complex frequency signal to a trunk line in an electronic switching system.

[Technical Challenges to Invent]

It solves the problem that the receiving side incorrectly recognizes the dual tone complex frequency signal as the voice signal noise or ambient noise is mixed when the dual tone complex frequency signal is transmitted.

[Summary of the solution of the invention]

In the method for transmitting a dual tone complex frequency signal according to the present invention, when an extension subscriber of an electronic switching system dials a telephone number of an external subscriber, the dual tone complex frequency signal generates a dual tone complex frequency signal corresponding to the dialed telephone number. Generating a complex frequency signal for transmitting the generated dual tone complex frequency signal to a trunk line, and transmitting the generated dual tone complex frequency signal from a predetermined time before transmitting the generated dual tone complex frequency signal. Thereafter, a system muting process for muting the system during the exchange until a predetermined time.

[Important Uses of the Invention]

Telephones connected to key phone systems or private switching systems

Description

How to send dual tone complex frequency signal in electronic switching system

1 is a block diagram of a general electronic switching system

Figure 2 is a dual tone complex frequency signal transmission waveform according to the conventional method

3 is a diagram for explaining a duplex tone frequency signal transmission operation according to the present invention.

4 is a dual-tone complex frequency signal transmission waveform according to the present invention

* Explanation of symbols for main parts of the drawings

100: central processing unit 102: memory unit

104: clock circuit 106: switching circuit

112: key phone subscriber circuit 116: trunk line circuit

120: dual tone complex frequency (DTMF) transmitter 130: key-phone telephone

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic switching system, and more particularly, to a method for transmitting a dual tone multi frequency (hereinafter referred to as DTMF) signal without causing an error in a trunk line.

Typically, when an extension subscriber of a key phone or a general telephone dials a telephone number of an external subscriber, a key phone system or a private switching system (hereinafter referred to as an electronic switching system) is used to dial a telephone number using a DTMF transmitter built into the system. A corresponding DTMF signal is generated and sent to CO.

FIG. 1 is a diagram showing the configuration of a general electronic switching system for performing such an operation. Referring to FIG. 1, the central processing unit 100 controls the overall operation of the system to control call switching and provide various services to a user. To control.

The memory unit 102 stores programs and initial service data of the central processing unit 100 for performing basic calls and various functions, and temporarily stores data processed by the central processing unit 100. The memory unit 102 includes a room for storing program and service data and a RAM for temporarily storing data generated during program execution. The clock circuit 104 generates current time data as the clock chip IC and outputs the current time data to the CPU 100. The switching circuit 106 switches various tones and voice data under the control of the CPU 100.

The general subscriber circuit 108 supplies the call current to the general telephones A, B, C, D under the control of the central processing unit 100, and at the same time, the general telephones A, B, C, D and the switching circuit. Interface the signals between 106. The ring generator 110 generates a ring signal and supplies the ring signal to the subscriber line. The key phone subscriber circuit 112 transmits and receives various data to and from the key phone telephones E, F, G, and H under the control of the central processing unit 100, and supplies a call current to the key phone telephones E, F, and G. H) and the signal between the switching circuit 106 are interfaced. Here, the key phone telephones E, F, G, H and general telephones A, B, C, D become extension subscribers. The line connecting the general subscriber circuit 108 and the key subscriber subscriber circuit 112 to the extension subscriber becomes a subscriber line.

The tone generator 114 generates various tone signals under the control of the central processing unit 100 and outputs them to the switching circuit 106. The trunk line circuit 116 forms a trunk line call loop by scissing the trunk line under the control of the central processing unit 100, and interfaces signals between the trunk line and the switching circuit 106. Here, the trunk line refers to a line connecting the trunk line circuit 116 and the national exchange.

The DTMF receiver 118 analyzes the DTMF signal input from the switching circuit 106, converts the DTMF signal into digital data, and outputs the digital data to the CPU 100. Here, the DTMF signal received by the switching circuit 106 by the DTMF receiver 118 may be a telephone number generated by an external subscriber through the trunk line or may be a telephone number generated by an extension subscriber. The DTMF transmitter 120 converts the digital data output from the CPU 100 into a DTMF signal and outputs the DTMF signal to the switching circuit 106.

As described above, when the extension subscriber dials the telephone number of the external subscriber, the central processing unit 100 controls the DTMF transmitter 120 to generate a DTMF signal corresponding to the dialed telephone number, and then outputs the generated DTMF signal. Applied to the trunk line circuit 116 to be sent to the trunk line. At this time, since the DTMF signal has the same frequency band as the voice signal, there was a problem in that the number to be dialed was not correctly dialed due to voice or ambient noise applied through the subscriber's talker or microphone. This problem has deteriorated the reliability of the telephone or system, causing many users complaints.

In order to solve the above problem, the conventional electronic switching system uses a mute process so that a voice signal or ambient noise cannot be transmitted through a trunk line when dialing.

FIG. 2 is a diagram showing an example of transmitting a DTMF signal according to the conventional method, and FIG. 2A shows an example of a DTMF signal generated by the DTMF transmitter 120. As shown in FIG. When a DTMF signal such as FIG. 2A is generated, the central processing unit 100 mutes all other components except the DTMF transmitter 120 as shown in FIG. 2B so that only the DTMF signal is routed to the trunk line. To be sent. However, since the mute processing is based on the time point at which the DTMF signal is transmitted and the time point at which the DTMF signal is not transmitted, the voice signal and the ambient noise are not completely blocked.

That is, according to the conventional method, there is a possibility that a voice signal or ambient noise may be mixed when the mute processing section transitions. FIG. 2C is a diagram showing that noise is mixed in a signal sent to the trunk line during the transition of the mute processing section. Reference numeral 200 indicates that the DTMF signal is normally transmitted without mixing noise. However, reference numeral 210 indicates that noise has been mixed and transmitted in the DTMF signal. Reference numerals 211 and 212 denote sections in which noise is mixed in the DTMF signal as the mute processing sections transition.

In this way, when the DTMF signal mixed with noise is transmitted, other electronic switching systems connected through trunk lines may recognize the phone numbers of other external subscribers, or the telephone numbers of two external subscribers. In some cases, it is not recognized. Accordingly, there is a problem that the extension subscriber can not make a call with the desired external subscriber.

Accordingly, an object of the present invention is to provide a method for transmitting a DTMF signal to a trunk line without occurrence of an error in an electronic switching system.

In accordance with the above object, the present invention provides a DTMF signal generation process for generating a DTMF signal corresponding to the dialed telephone number when the extension subscriber of the electronic switching system dials the telephone number of the external subscriber, and the generated DTMF DTMF transmission process for transmitting a signal to a trunk line, and a system muting process for muting the exchange system from a predetermined time before transmitting the generated DTMF signal to a predetermined time after transmitting the generated DTMF signal. Towards the DTMF signal transmission method.

DETAILED DESCRIPTION A detailed description of preferred embodiments of the present invention will now be described with reference to the accompanying drawings. The configuration of the electronic exchange system for carrying out the present invention is the same as that in FIG. 1, and the reference numerals are the same. However, the central processing unit 100 of FIG. 1 has a guard time before and after the time when the DTMF signal corresponding to the dial digit is transmitted, and the DTMF signal is transmitted after a certain time before the DTMF signal is transmitted. Control the operation of muting the system by time.

Referring now to FIG. 3, there are shown the components of FIG. 1 for efficiently performing the operation of transmitting DTMF signals in accordance with the present invention, wherein the waveforms of DTMF signals transmitted are shown in FIG. Although only the key phone telephone 130 is shown in FIG. 3, this is for effectively explaining the present invention and does not mean that the present invention is limited to the key phone telephone.

That is, it should be noted that the present invention can be applied to not only a key phone but also a general phone.

First, when an extension subscriber presses a dialable button on the key phone telephone 130 of FIG. 3 for a call with an external subscriber, the corresponding data is transferred to the central processing unit via the data interface 112B of the key phone subscriber circuit 112. 100). The central processing unit 100, which has received the data to be dialed to the trunk line by the key phone telephone 130, inspects the trunk line CO connected through the trunk line circuit 116 and allocates the trunk line in the dormant state, and allocates the trunk line. The confirmation sound indicating that the phone is sent to the phone 130.

Next, when the extension subscriber of the key phone telephone 130, which recognizes that the CO line is allocated from the transmitted confirmation tone, continues to press the telephone number digit of the external subscriber, the central processing unit 100 displays the pressed telephone number digit. Is stored in the dial buffer of the memory unit 102, and the DTMF transmitter 120 is operated to generate a DTMF signal corresponding to the pressed telephone number digit.

The DTMF signal generated as described above is a signal of the form as shown in FIG. 4A, and the DTMF signal is transmitted to the trunk line C.O via the switching circuit 106 and the trunk line circuit 116.

The sending operation of the DTMF signal is performed as the central processing unit 100 controls the switching circuit 106. That is, when the central processing unit 100 controls the first port # 1 and the third port # 3 of the switching circuit 106 to be connected, the DTMF signal is transmitted through the trunk line circuit 116. Is sent out. However, the central processing unit 100 also performs an operation of muting the system for a predetermined time before sending the DTMF signal and for a predetermined time after sending the DTMF signal. That is, the central processing unit 100 switches the switching circuit from T1 time (guard time) before the DTMF signal is transmitted to T2 time (guard time) after the DTMF signal is transmitted as shown in FIG. 4 (B). The connection between the second port (# 2) and the third port (# 3).

The system mute operation to which the guard time is applied as described above is a characteristic element of the present invention for transmitting the DTMF signal without the occurrence of an error, and the DTMF signal is transmitted to the CO line by this operation. The noise of the voice signal mixed through the transmitter and the microphone is blocked, and the noise generated in the system is also blocked. The guard time is preferably set to a value in the range of 50 ~ 100ms.

When the DTMF signal is transmitted by applying the guard time as described above, the DTMF signal transmitted has the form as shown in FIG. Referring to FIG. 4C, reference numerals 400, 420, 430, and 450 indicate that only noise generated as the mute operation of the system is transitioned, and reference numerals 410, 440 indicate that the DTMF signal is normally transmitted. Even with this method, the noise can be transmitted to the trunk line, but since it is separated from the DTMF signal sent to the digit, the receiver can receive the digit without error because it does not affect the DTMF signal sent to the digit. In addition, the noise that is likely to be generated also generates a short time, so that the receiving side may not recognize the digit incorrectly.

As described above, by processing the system mute operation that applies the guard time when transmitting the DTMF signal, the DTMF signal can be transmitted without error, and the subscriber can also talk to the desired external subscriber.

Claims (4)

A method for transmitting a dual tone complex frequency (DTMF) signal in an electronic switching system, comprising: a dual tone complex frequency signal that generates a dual tone complex frequency signal corresponding to the dialed telephone number when an extension subscriber dials a telephone number of an external subscriber; Generating a frequency signal, transmitting a generated dual tone complex frequency signal to a trunk line to which the system is connected, and generating the generated dual tone complex frequency signal from a predetermined time before transmitting the generated dual tone complex frequency signal Method for transmitting a dual tone composite frequency signal comprising a system muting process of muting the switching system until a predetermined time after transmitting the dual tone composite frequency signal The system of claim 1, wherein the system muting process comprises: switching between 50 and 100 milliseconds before transmitting the generated dual tone complex frequency signal to 50 and 100 milliseconds after transmitting the generated dual tone complex frequency signal. A dual tone complex frequency signal transmitting method, characterized in that the system is muted. A telephone and a dual tone complex frequency signal generating means for generating a dual tone complex frequency (DTMF) signal, the method for transmitting a dual tone complex frequency signal in an electronic switching system connected to a trunk line through a trunk line circuit, A dual tone complex frequency signal generating process of generating a dual tone complex frequency signal corresponding to the pressed telephone number by using the dual tone complex frequency signal generating means when the telephone number of an external subscriber is pressed on the mobile terminal; A duplex tone frequency signal sending step of sending the generated duplex tone frequency signal to the trunk line by connecting a complex frequency signal generating means and the trunk line circuit, and a predetermined time before transmitting the generated duplex tone frequency signal; The duotone until a predetermined time after transmitting the generated duotone complex frequency signal; A dual tone complex frequency signal transmitting method, comprising: a trunk line circuit blocking process for interrupting a connection between a complex frequency signal generating unit and the trunk line circuit; The method of claim 3, wherein the trunk line disconnection process comprises: 50 to 100 milliseconds before transmitting the generated dual tone complex frequency signal to 50 to 100 milliseconds after transmitting the generated dual tone complex frequency signal. And a duplex tone frequency generator, characterized in that the connection between the duplex tone frequency generator and the trunk line circuit is interrupted.