Apparatus for reducing echoes and noises in telephone

An apparatus for reducing echoes which are generated due to signals induced to a handset connector in a telephone, includes a round-type handset connector cord arranged into a round configuration having a certain arrangement of the speech transmitting and receiving lines, and a connecting unit provided in the body of the telephone and having a differential amplifier for applying signals received to a transmitting unit by differentially amplifying the signals. Alternatively, the apparatus for reducing echoes includes a flat-type handset connector cord having the lines arranged in a certain order, and a connecting unit for connecting the speech transmitting and receiving lines in certain manner. Alternatively, the apparatus for reducing echoes and noises includes a flat-type handset connector cord having the lines arranged in a certain order, and a connecting unit connecting to the speech-transmitting lines and the speech-receiving lines in a certain manner.

CLAIM OF PRIORITY

This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from my application entitled DEVICE FOR REDUCING ECHO AND NOISE IN PHONE earlier filed with the Korean Industrial Property Office on Dec. 4, 2001 and there duly assigned Serial No. 2001-76157.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a telephone, and more particularly, to an apparatus for reducing echoes and noises.

2. Description of the Related Art

Generally in a wire or wireless system such as VoIP (Voice Over Internet Protocol) causing delay by a large amount, a transmitted signal evidently has echoes. As the echoes occur like this, when a speaker in a telephone outputs a voice of a far end talker, the voice is heard not only to a near end talker but also to the far end talker obstructing conversation since the voice is inputted via a microphone and then undergoes feedback toward the far end talker through several passages of a communication channel.

In a wire telephone in a Public Switched Telephone Network (PSTN), the created echoes rarely create any delay. On conversation via a handset, the echoes are not clearly heard or discriminated to a user covered with sidetone. Thus, the echoes may not cause any serious problems.

On the contrary, since a VoIP telephone or a mobile telephone may have the delay by a large degree, the quality of conversation is degraded due to the echoes in such a degree that it can be definitely recognized.

Classifying the echoes according to the cause of generation, the echoes include side-tone, induced echo, acoustic echo and the like, in which the side-tone is an echo generated by inputting a portion of a signal on a speech-transmitting again into a speech-receiving channel in the telephone for obtaining natural voice conversation, the induced echo is generated due to induction in a communication line or handset connector cord, and the acoustic echo is generated since a voice from a speaker in a receiving terminal is inputted into a microphone again.

In the above echoes, the sidetone is intentionally generated and thus has no problem. The acoustic echo is reduced by using an echo canceller with a Digital Signal Processor (DSP) in general.

In the telephone, the handset connector cord generally uses a flat-type curl cord having a pair of speech-transmitting lines and a pair of speech-receiving lines arranged in parallel. The cord is long enough to reach 2 or 3 m (meters) when the curl is unwound. Therefore, a signal in the speech-receiving line is induced to the speech-transmitting line by a large amount causing the echo so that the counterpart of the conversation can hear his or her own voice after a certain time period lapses.

The construction of a typical telephone connected to a handset is as follows. A telephone body and a handset are connected by a flat-type handset connector cord, in which only a speech-transmitting unit, a speech-receiving unit and a connecting unit of the telephone body are shown. The connecting unit has a pair of speech-transmitting line terminals Tx+ and Tx− and a pair of speech-receiving line terminals Rx+ and Rx−, in which the speech-transmitting line terminals Tx+ and Tx− are connected to the speech-transmitting unit. On the other hand, one of the speech-receiving line terminal Rx+ is connected to the speech-receiving unit, and the other one of the speech-receiving line terminal Rx− is connected to the ground. The speech-transmitting line terminal Tx+ is applied with a bias voltage Vref via a resistance R1. The handset connector cord joining the connecting unit to connect the handset to the telephone body includes a pair of speech-transmitting lines connecting to a microphone in the handset and a pair of speech-receiving lines connecting to a speaker in the handset. The handset connector cord uses a flat-type curl cord in which the Tx+ speech-transmitting line, the Rx+ speech-receiving line, Rx− speech-receiving line and the Tx− speech-transmitting line are arranged in sequence. Also, a modular jack is generally used to connect between the connecting unit and the handset connector cord.

In the handset connector cord as set forth above, the Rx+ speech-receiving line and the Tx+ speech-transmitting line are arranged side-by-side adjacent to each other so that a signal along the Rx+ speech-receiving line may be induced toward the Tx+ speech-transmitting line due to an induced current to generate the echoes. Further, the speech-receiving side is in the low impedance state and thus hardly influenced by external noises. On the other hand, the speech-transmitting side is in the high impedance state and thus readily influenced by even a small amount of the external noises.

SUMMARY OF THE INVENTION

Accordingly, the present invention has been made to solve the foregoing and other problems and it is an object of the present invention to provide an apparatus capable of reducing echoes which are generated due to signals induced to a handset connector cord in a telephone.

It is another object of the invention to provide an apparatus capable of reducing echoes as well as noises which are generated due to signals induced to a handset connector in a telephone.

It is still another object of the present invention to provide an apparatus capable of reducing echoes or both echoes and noise that are generated due to signals induced to a handset connector in a telecommunication device, and yet is easy and inexpensive to manufacture and implement.

According to an aspect of the invention to obtain the above and other objects, an apparatus is provided for reducing echoes in a telephone, including: a round-type handset connector cord arranged into a round configuration and having Tx+ and Tx− speech-transmitting lines and Rx+ and Rx− speech-receiving lines for connecting a handset to a body of the telephone with the Tx+ and Tx− speech-transmitting lines being connected to a microphone of a handset and the Rx+ and Rx− speech-receiving lines being connected to a speaker of the handset, wherein the Tx+ and Tx− speech-transmitting lines are opposed to each other, and each of the Rx+ and Rx− speech-receiving lines alternates with each of the Tx+ and Tx− speech-transmitting lines; and a connecting unit provided in the body of the telephone and having a differential amplifier for applying signals received via the Tx+ and Tx− speech-transmitting lines to a transmitting unit by differentially amplifying the signals, wherein the connecting unit connects the Tx+ speech-transmitting line to a non-inversion input terminal of the differential amplifier, the Tx− speech-transmitting line to an inversion input terminal of the differential amplifier, the Rx+ speech-receiving line to a speech receiving unit, and the Rx− speech-receiving line to the ground.

According to another aspect of the invention to obtain the above and other objects, an apparatus is provided for reducing echoes in a telephone, including: a flat-type handset connector cord having Tx+ and Tx− speech-transmitting lines and Rx+ and Rx− speech-receiving lines for connecting a handset to a body of the telephone with the Tx+ and Tx− speech-transmitting lines being connected to a microphone of a handset and the Rx+ and Rx− speech-receiving lines being connected to a speaker of the handset, wherein the lines are arranged in the order of the Tx+ speech-transmitting line, the Rx+ speech-receiving line, the Rx− speech-receiving line, the Tx− speech-transmitting line; and a connecting unit provided in the body of the telephone for connecting the Tx+ speech-transmitting line to a speech-transmitting unit, the Rx− speech-receiving line to a speech-receiving unit, the Rx+ speech-receiving line and the Tx− speech-transmitting line to the ground.

According to yet another aspect of the invention to obtain the above and other objects, an apparatus is provided for reducing echoes and noises in a telephone, including: a flat-type handset connector cord having Tx+ and Tx− speech-transmitting lines and Rx+ and Rx− speech-receiving lines for connecting a handset to a body of the telephone with the Tx+ and Tx− speech-transmitting lines being connected to a microphone of a handset and the Rx+ and Rx− speech-receiving lines being connected to a speaker of the handset, wherein the lines are arranged in the order of the Rx+ speech-receiving line, the Rx− speech-receiving line, the Tx+ speech-transmitting line, and the Tx− speech-transmitting line; and a connecting unit provided in the body of the telephone for connecting the Tx+ speech-transmitting line to a speech-transmitting unit, the Rx− speech-receiving line to a speech-receiving unit, the Rx+ speech-receiving line and the Tx− speech-transmitting line to the ground.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Turning now to the drawings,FIG. 1illustrates the construction of a general telephone connected to a handset.FIG. 1illustrates that a telephone body100and a handset102are connected by flat-type handset connector cord104, in which only a speech-transmitting unit106, a speech-receiving unit108and a connecting unit110of the telephone body100are shown. As shown inFIG. 1, the connecting unit110has a pair of speech-transmitting line terminals Tx+ and Tx− and a pair of speech-receiving line terminals Rx+ and Rx−, in which the speech-transmitting line terminals Tx+ and Tx− are connected to the speech-transmitting unit106. On the other hand, one of the speech-receiving line terminals Rx+ is connected to the speech-receiving unit108, and the other one of the speech-receiving line terminals Rx− is connected to the ground. The speech-transmitting line terminal Tx+ is applied with a bias voltage Vref via a resistance R1. The handset connector cord104joining the connecting unit110to connect the handset102to the telephone body100includes a pair of speech-transmitting lines112and118connecting to a microphone (not shown) in the handset102and a pair of speech-receiving lines114and116connecting to a speaker (not shown) in the handset102. The handset connector cord104uses a flat-type curl cord in which the Tx+ speech-transmitting line112, the Rx+ speech-receiving line114, Rx− speech-receiving line116and the Tx− speech-transmitting line118are arranged in sequence as shown in FIG.2. Also, a modular jack is generally used to connect between the connecting unit110and the handset connector cord104.

In the handset connector cord104as set forth above, the Rx+ speech-receiving line114and the Tx+ speech-transmitting line112are arranged side-by-side adjacent to each other so that a signal along the Rx+ speech-receiving line114may be induced toward the Tx+ speech-transmitting line112due to an induced current to generate the echoes. Further, the speech-receiving side is in the low impedance state and thus hardly influenced by external noises. On the other hand, the speech-transmitting side is in the high impedance state and thus readily influenced by even a small amount of the external noises.

The following detailed description will present a preferred embodiment of the invention in reference to the accompanying drawings, in which well-known functions or constructions will not be described in detail since they would unnecessarily obscure the understanding of the invention.

FIG. 3is a block diagram illustrating the construction of an apparatus for reducing echoes according to a preferred embodiment of the invention.

Referring toFIG. 3, a connecting unit204having a differential amplifier206is used in a telephone body200instead of the foregoing connecting unit110in the telephone body100shown inFIG. 1. Around-type handset connector cord202is adopted as shown in FIG.4(a). In the connecting unit204, speech-receiving line terminals Rx+ and Rx− are respectively connected to a speech-receiving unit108and the ground in the same manner as in FIG.1. On the other hand, the differential amplifier206is installed between a speech-transmitting unit106and speech-transmitting line terminals Tx+ and Tx−. A Tx+ speech-transmitting line112is connected to a non-inversion input terminal (designated with +) of the differential amplifier206while a Tx− speech-transmitting line118is connected to an inversion input terminal (designated with −) of the differential amplifier206. Accordingly, the differential amplifier206applies signals received via the Tx+ and Tx− speech-transmitting lines112and118to the speech-transmitting unit106by differentially amplifying the signals. In this case, the signals induced from the Rx+ speech-receiving line114to the Tx+ and Tx− speech-transmitting lines112and118are cleared since they are inputted into the differential amplifier206with the same phase and magnitude.

When the flat-type handset connector cord104as shown inFIG. 2is used, a signal induced to the Tx+ speech-transmitting line is larger than a signal induced to the Tx− speech-transmitting line since the Rx+ speech-receiving line and the Tx+ speech-transmitting line are adjacent to each other while the Rx− speech-receiving line is arranged between the Rx+ speech-receiving line and the Tx− speech-transmitting line. This rarely has an effect that clears the echoes. Therefore, in order to make the signal induced to the Tx+ speech-transmitting line to have the same magnitude as that induced to the Tx− speech-transmitting line, the round-type handset connector cord202is adopted as shown in FIG.4(a). As shown in FIG.4(a), the handset connector cord202has the lines which are roundly arranged so that the Tx+ and Tx− speech-transmitting lines112and118are opposed to each other while the Rx+ and Rx− speech-receiving lines114and116are alternating with the Tx+ and Tx− speech-transmitting lines112and118, respectively. When seen clockwise in FIG.4(a), the lines are roundly arranged in the order of the Tx+ speech-transmitting line112, the Rx− speech-receiving line116, the Tx− speech-transmitting line118and the Rx+ speech-receiving line114.

Using the round-type handset connector cord202, as shown in FIG.4(a), makes the interval between the Rx+ speech-receiving line114and the Tx+ speech-transmitting line112be the same as the interval between the Rx+ speech-receiving line114and the Tx− speech-transmitting line118so that the signals induced by the Tx+ and Tx− speech-transmitting lines112and118have the same magnitude. Therefore, the signals induced to the Tx+ and Tx− transmitting-lines112and118by the differential amplifier206are so offset to clear almost all of the echoes.

In the meantime, in the actual manufacture of the round-type handset connector cord202as shown in FIG.4(a), the round-type handset connector cord may be readily disarranged as shown in FIG.4(b) even though the degree of the disarrangement is different. As seen in FIG.4(b), for example, the interval between adjacent lines such as the interval between the Rx+ speech-receiving line114and the Tx+ speech-transmitting line112might not be the same as the interval between the Rx+ speech-receiving line114and the Tx− speech-transmitting line118in the disarranged round-type handset connector cord202′. When the round-type handset connector cord is disarranged as shown in FIG.4(b), the effect of reducing the echoes will be decreased.

FIG. 5is a block diagram illustrating the construction of an apparatus for reducing echoes according to an alternative embodiment of the invention in regard to the above description in order to reduce the echoes with the conventional flat-type handset connector cord104shown in FIG.2. The echo-reducing apparatus inFIG. 5is constituted by adopting a connecting unit302in a telephone body300instead of the foregoing connecting unit110in the telephone body100shown in FIG.1. In the telephone body300, a speech-receiving line terminal Rx− is connected to a speech-receiving unit108unlike the conventional speech-receiving line terminal Rx− connected to the ground inFIG. 1, and a speech-transmitting line terminal Tx− is connected to the ground unlike the conventional speech-transmitting line terminal Tx− connected directly to the speech transmitting unit106in FIG.1. A speech-transmitting line terminal Tx+ is connected to a speech-transmitting unit106in the same manner as in FIG.1. Therefore, a Tx+ speech-transmitting line112is connected to a speech-transmitting unit106, an Rx− speech-receiving line116is connected to the speech-receiving unit108, and an Rx+ speech-receiving line114and a Tx− speech-transmitting line118are connected to the ground. Although the Rx+ speech-receiving line114is connected to the ground and the Rx− speech-receiving line116is connected to the speech-receiving unit108unlike the above construction shown inFIG. 1, a speaker10in the handset102will normally operate as usual since the speaker10can operate regardless of the signal Rx+ or Rx− inputted therein. Further, although the Tx− speech-transmitting line118is connected to the ground instead of the speech-transmitting unit106, the Tx+ speech-transmitting line112is connected to a microphone20in the handset102so that the microphone20may normally operate as usual.

As set forth above, as the Tx− speech-transmitting line118is connected to the ground, a signal induced to the Tx− speech-transmitting line118from the Rx− speech-receiving line116is grounded. As the Tx+ speech-transmitting line112is adjacent to the Rx+ speech-receiving line114connected to the ground, a signal from the Rx− speech-transmitting line116is not induced to the Tx+ speech-transmitting line112. This prevents the feedback of a signal from the speech-receiving unit108to the speech-transmitting unit106thereby reducing the echoes by a large amount.

In the meantime, in consideration that the speech-receiving side is in the low impedance state and thus will be hardly influenced by external noises while the speech-transmitting side is in the high impedance state and thus will be readily influenced by even a small amount of the external noises, it is preferred to reduce noises as well as the echoes.

FIG. 6is a block diagram illustrating the construction of an apparatus for reducing echoes and noises according to the invention, in which a flat-type handset connector cord402is used instead of the conventional handset connector cord104shown in FIG.1. Referring toFIGS. 6 and 7, the flat-type handset connector cord402has lines arranged in the order of an Rx+ speech-receiving line406, an Rx− speech-receiving line408, a Tx+ speech-transmitting line410and a Tx− speech-transmitting line412. In the echo and noise-reducing apparatus of the invention, a telephone body400has a connecting unit404so constituted to correspond to the construction of the flat-type handset connector cord402. In the connecting unit404, a speech-transmitting line terminal Tx+ is connected to the speech-transmitting unit106, a speech-receiving line terminal Rx+ is connected to the speech-receiving unit108, and speech-transmitting line terminal Tx− and a speech-receiving line terminal Rx− are connected to the ground. Accordingly, a Tx+ speech-transmitting line410is connected to the speech-transmitting unit106, the Rx+ speech-receiving line406is connected to the speech-receiving unit108, and the Tx− speech-transmitting line412and the Rx− speech-receiving line408are connected to the ground.

The connecting unit404and the handset connector cord402as set forth above do not correspond to the arrangement of terminals of the microphone and speaker in the conventional handset102as shown in FIG.1. So it is necessary to adopt an exclusive-purpose handset414having a terminal arrangement corresponding to that of the connecting unit404and the handset connector cord402of the invention. In using the exclusive handset414, the Tx+ speech-transmitting line410is placed between the Rx− speech-receiving line408and the Tx− speech-transmitting line412resultantly preventing a signal from being induced from the Rx+ speech-receiving line406to the Tx+ speech-transmitting line410. This accordingly prevents the signal from the speech-receiving unit108that may return to the speech-transmitting unit106due to the feedback thereby reducing the echo by a large amount while reducing the noises flowing to the speech-transmitting unit106by a large amount.

As set forth above, the present invention have the following advantages. The same magnitude of signals are induced to the Tx+ and Tx− transmitting lines from the speech-receiving lines and the echoes are cleared through the differential amplification so as to reduce the echoes due to the signals induced between the lines of the handset connector cord. Further, the line arrangement of the handset connector cord is modified from that of the conventional handset connector cord so as to reduce the echoes due to the signals induced between the handset connector cord lines and the noises also.

Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions can be made without departing from the scope and spirit of the invention as disclosed in the accompanying claims.