JP2646962B2 - Voice addition circuit and test method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voice adding circuit for adding a plurality of input PCM signals in a voice band supplied from a plurality of transmitters and compressed by .mu.-law and transmitting the sum to one receiver. In particular, the present invention relates to a method of performing a line test including a function test of a voice addition circuit.

[0002]

2. Description of the Related Art FIG. 2 shows a configuration of a conventional voice adding circuit and a test method thereof. As shown in FIG.
The first to n-th decoders 11,..., 1j,.
It has an adder 20 and a coder 30 '. Hereinafter, the PCM signal in the audio band compressed by the μ-law is simply referred to as the μ signal. The first to n-th input μ signals are supplied to the first to n-th decoders 11 to 1n from the first to n-th transmitters, respectively. The first to n-th decoders 11 to 1n respectively convert the first to n-th input μ signals into first to n-th PCM linear signals. These first to n-th PCM linear signals are supplied to the adder 20. The adder 20 adds the first to n-th PCM linear signals, and outputs the added PCM linear signal. The added PCM linear signal is supplied to the coder 30 '. The coder 30 'converts the added PCM linear signal into an output μ signal. This output μ signal is supplied to one receiver.

As is well known, the μ signal has two positive and negative 0 levels. Therefore, to convert a plurality of μ signals to multiple PCM linear signal, the after adding them,
It cannot be determined whether the 0 level of the input μ signal is positive or negative. That is, the conventional voice adding circuit cannot pass a specific pattern (a negative 0 level μ signal). For this reason, a random digital pattern cannot be used for a line test including a conventional voice addition circuit.

[0004] Two testers 60 'and 70 are used to test a line containing a conventional voice summing circuit. The tester 60 'is a test signal generator for generating a .mu. Signal having a level other than the negative 0 level as a test signal. The tester 70 is a test signal measuring device for measuring the level of the μ signal.

Hereinafter, a conventional method for testing a line including a voice adding circuit will be described. The test signal is input from the tester 60 'to the line P to be tested. Here, it is assumed that the line P is connected to the j-th (1 ≦ j ≦ n) decoder 1j. Here, the line P is connected to the first to n-th decoders 11 to 1
n. At the time of the line test, a 0-level μ signal is input to lines other than the line P. The test signal generated from the tester 60 'is converted into a PCM linear signal by the j-th decoder 1j, added by the adder 20, and converted into a μ signal by the coder 30'. The level of the μ signal is measured by the tester 70, and by confirming that it matches the level of the test signal, the conduction of the line P is determined.

[0006]

As described above, the conventional line test method has the following disadvantages when the line on which the line test is performed has a conventional voice addition circuit.
A random digital pattern cannot be used as a test signal. When performing a line test, it must be determined whether the line to be tested is a line having a voice addition function. A tester (test signal generator) different from a tester (test signal generator) used in a normal line test is required.

Accordingly, it is an object of the present invention to provide a voice adding circuit that can use a random digital pattern as a test signal.

[0008]

A voice adding circuit according to the present invention is provided for a voice band supplied from a plurality of transmitters and compressed by .mu.-law (a companding rule having two positive and negative 0 levels). of a plurality of input PCM signals into their respective multiple PCM linear signal, and adding a plurality of PCM linear signal,
This added PCM linear signal is converted again into an output PCM signal of a voice band compressed according to μ-law (compression expansion rule), and the output PCM signal is transmitted to one receiver. Note that the first to n-th PCM linear signals are
For example, it can be represented by two's complement.

According to the present invention, a judging means for judging whether or not any of a plurality of input PCM signals has a sign bit indicating a negative value, and a means for judging whether the added PCM linear signal is 0 or not. A detection means for detecting that the signal level is at a level, and if any of a plurality of input PCM signals has a sign bit indicating a negative value and the added PCM linear signal is at a 0 level, 0-level μ-la
means for outputting, as an output PCM signal, a PCM signal in the audio band compressed by w (the companding rule).

[0010]

When testing a line including a voice adding circuit, a random digital pattern is input as a test signal to a line to be tested, and the other lines are compressed according to a positive 0-level μ-law (the above companding rule). The PCM signal of the specified voice band is input.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

Referring to FIG. 1, a description will be given of a voice adding circuit and a test method thereof according to an embodiment of the present invention. The illustrated voice addition circuit has a sign determination circuit 40 and a zero level detector 50, and has the same configuration as that shown in FIG. 2 except that the coder is changed as described later. Thus, the coder is given the reference numeral 30 and
Components having the same functions as the components shown in FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted.

The code determination circuit 40 includes first to n-th PCMs output from the first to n-th decoders 11 to 1n.
Code bits S1 to Sn of the linear signal are supplied. The sign determination circuit 40 determines whether there is one or more negative sign bits in the sign bits S1 to Sn. Sign bit S1
If there is one or more negative sign bits in .about.Sn, the sign judging circuit 40 outputs a negative sign judging signal. In this example, the sign determination circuit 40 is constituted by an AND gate.

The 0 level detector 50 detects whether the added PCM linear signal is a 0 level signal. When the added PCM linear signal is a 0-level signal, the level detector 50 outputs a 0-level detection signal.

The coder 30 adds the P
When the CM linear signal is supplied, the sign determination circuit 40
And the level detector 50. A 0-level detection signal from the level detector 50 and a sign determination circuit 4
When receiving a negative sign determination signal from 0, the coder 30 outputs a negative 0 level μ signal as an output μ signal. Also,
When receiving the 0 level detection signal from the level detector 50 but not receiving the negative sign determination signal from the sign determination circuit 40, the coder 30 outputs a positive 0 level μ signal as the output μ signal. If it does not receive a zero level detection signal from the level detector 50, the coder 30 will, in the usual way, add the added P
The CM linear signal is converted into an output μ signal.

Two testers 60 and 70 are used to test the line including the voice adding circuit of the present embodiment.
The tester 60 is a test signal generator that generates a μ signal (random digital pattern) having an arbitrary level as a test signal. The tester 70 is a test signal measuring device for measuring the level of the μ signal.

Next, a description will be given of a method of testing a line including the voice adding circuit according to the present embodiment. The μ signal is input from the tester 60 to the line P to be tested. Here, the line P is the j-th
It is assumed that the decoder 1j is connected to (1 ≦ j ≦ n). The line P can be connected to any of the first to n-th decoders 11 to 1n. During the line test, a positive 0 level μ signal is input to lines other than the line P. The μ signal generated from this tester 60 is supplied to the j-th decoder 1j by P
The signal is converted into a CM linear signal, added by an adder 20, and converted into a μ signal by a coder 30. Here, when a negative 0 level μ signal is input as a test signal from the tester 60, the coder 30 also outputs a negative 0 level μ signal. Therefore, there is no digital pattern that cannot be passed in the line test.

According to this method, a random digital pattern is input from the tester 60 to the line P to be tested, and a positive 0-level μ signal is input to the other lines, so that the line P has no error. Can pass through random digital patterns.

Although the present invention has been described with reference to the embodiments, the present invention is not limited to the above-described embodiments, and it is needless to say that various changes / modifications can be made without departing from the gist of the present invention. is there.

[0020]

As described above, according to the present invention, a random digital pattern can be passed through a line to be tested in a line test including the voice adding circuit according to the present invention.
Further, when performing a line test, it is not necessary to determine whether the line to be tested is a line having a voice addition function. Further, the same tester as that used in a normal line test can be used.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a voice addition circuit and a test method thereof according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a conventional voice addition circuit and a test method thereof.

[Explanation of symbols]

 P Arbitrary line 11-1n Decoder 20 Adder 30 Coder 40 Code judging circuit 500 0 Level detecting circuit 60 Tester (test signal generator) 70 Tester (test signal measuring device)

Claims (4)

(57) [Claims] 1. A micro-law supplied from a plurality of speakers.
A plurality of input PCM signal of the compressed voice band converted into its <br/> Resolution Re multiple PCM linear signal by said plurality of P
In a voice addition circuit that adds the CM linear signal, converts the added PCM linear signal into an output PCM signal of a voice band compressed by the μ-law again, and transmits the output PCM signal to one receiver. Determining means for determining whether or not any of the plurality of input PCM signals has a sign bit indicating a negative value; and detecting that the added PCM linear signal is at a 0 level. Detecting means, if any of the plurality of input PCM signals has a sign bit indicating a negative value, and if the added PCM linear signal is at a zero level, the μ Means for outputting, as the output PCM signal, a PCM signal of an audio band compressed by -law. 2. A method for testing a line including an audio adding circuit according to claim 1, wherein a random digital pattern is input as a test signal to a line to be tested, and a positive 0 level μ-law is input to another line. A PCM signal of a voice band compressed by the method described above. 3. A supplied from the plurality of the speaker, 0 level converted to two voice band multiple input PCM signal, respectively it multiple PCM linear signal which has been compressed by the companding law present at the positive and negative Then, the plurality of PCM linear signals are added, and the added PCM linear signals are converted again into an output PCM signal of an audio band compressed according to the companding rule.
A voice adding circuit for transmitting an M signal to one receiver, a determining means for determining whether or not any of the plurality of input PCM signals has a sign bit indicating a negative value; Detecting means for detecting that the added PCM linear signal is at the 0 level; and any of the plurality of input PCM signals whose sign bit indicates a negative value, and wherein the added PCM linear signal is Means for outputting, as the output PCM signal, a PCM signal of a voice band compressed according to the companding rule of a negative 0 level, when the output PCM signal is at a 0 level. 4. A method for testing a line including an audio adder circuit according to claim 3, wherein a random digital pattern is input as a test signal to a line to be tested, and said companding signal having a positive 0 level is input to another line. A test method characterized by inputting a PCM signal of a voice band compressed according to the rule.