JPH0646467A - Signal detector for intra-band signal transmitter - Google Patents

Abstract

PURPOSE:To prevent the malfunction of the signal current in a signal transmitter which uses a specific frequency in a band as a signal for signal current. CONSTITUTION:A preventing circuit 4 prevents the signals f1 and f2 and calculates the band average value, and a signal detecting circuit 6 detects the signal f1 or f2. A comparator 8 compares the output of the circuit 4 with that of the circuit 6 in terms of the level and the time. Meanwhile a preventing circuit 5 prevents the signals f3 and f4 and calculates the band average value. A signal detecting circuit 7 detects the signal f3 or f4, and a comparator 9 compare the output of the circuit 5 with that of the circuit 7 in terms of the level and the time. furthermore a comparator 10 compares the output of the comparator 8 with that of the comparator 9 in terms of the level and the time. Then a switching circuit 11 selects a signal form out of the outputs of the comparators 8-10 in accordance with the state of a transmission line and the purpose of application.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal transmission device that uses a specific frequency within a band as a signal for a signal current, and more particularly to a signal detection device for an in-band signal transmission device that prevents malfunction of the signal current. .

In order to transmit a control signal or the like in a voice line, a signal having a specific frequency within a band is used as a signal current and the signal is transmitted, and a signal having this specific frequency is separated at a receiving side to reproduce a signal current. In-band signal transmission equipment is used.

As a signal detection method in such an in-band signal transmission device, it is necessary to prevent a malfunction of the signal current without being disturbed by an external wave or the like.

[0004]

2. Description of the Related Art FIG. 5 shows a conventional signal detection method in an in-band signal transmission apparatus, in which a delay circuit is added as a protection circuit to a one-frequency detection circuit. There is. In the figure, 801 is a band rejection filter of frequency f ₁ , 802, 803 are amplification circuits, 804, 805 are rectification circuits, 806 is a comparison circuit, 807 is a delay circuit, 80
Reference numeral 8 is a bandpass filter having a frequency f ₁ .

The signal current f _{1 at the} input (IN) is f
_The signal is extracted by the _1- bandpass filter 808, amplified by the amplifier circuit 802, rectified by the rectifier circuit 804, and becomes a DC signal, which is input to the comparison circuit 806.

On the other hand, signal components other than f ₁ are extracted through the band-elimination filter 801 for f ₁ , amplified by the amplifier circuit 803, rectified by the rectifier circuit 805, and have a polarity different from that of the rectifier circuit 804. And the comparison circuit 8
It is input to 06.

The comparison circuit 806 compares both inputs, and when the comparison result shows that the direct current signal based on f ₁ is large, inputs it to the delay circuit 807. The delay circuit 807 processes the input signal temporally, by the time length of the signal current f _1, to determine whether the components of f ₁ included in either or audio signal is a signal current, signal When it is a current, it produces a detection output.

FIG. 6 shows another conventional signal detection method in an in-band signal transmission device, which uses a signal current of two frequencies. 901, 9 in the figure
02 is a bandpass filter having frequencies f _{1 and} f ₂ , and 90
3, 904 is an amplifier circuit, 905, 906 are rectifier circuits, 9
Reference numeral 07 is an AND circuit, and 908 is a delay circuit.

The signal current f _{1 at the} input (IN) is f
_The signal is extracted by the _1- bandpass filter 901, amplified by the amplifier circuit 903, rectified by the rectifier circuit 905 into a DC signal, and input to the AND 907.

The signal current f _{2 at the} input (IN) is f
_The signal is extracted by the ₂ band pass filter 902, amplified by the amplifier circuit 904, rectified by the rectifier circuit 906 to be a DC signal, and input to the AND 907.

The AND circuit 907 is a rectifier circuit 905, 9.
The output is generated only when the outputs of 06 are simultaneously generated, that is, when the f ₁ signal and the f ₂ signal are simultaneously input. The delay circuit 908 corrects the signal waveform and adjusts it in time to generate a detection output.

[0012]

In the conventional signal detection method in the in-band signal transmission device shown in FIG.
Since it is a single frequency system, there are the following problems. (A) When talking, the f ₁ frequency component included in the voice signal may be detected as a signal current, which is one of the causes of malfunction of the terminal. (B) Since the delay circuit is provided to prevent malfunction, it takes time to process the signal current f ₁ from the other party.

The conventional signal detection method in the in-band signal transmission device shown in FIG. 6 does not have the above-mentioned drawbacks because it is a two-frequency method, but has the following problems. (A) Since there is no protection circuit, a malfunction occurs due to the same frequency component as the signal current in the audio signal. (B) A malfunction occurs due to the 2nd wave, the 3rd wave, etc. generated in the signal of the modulator / demodulator or the like.

[0014]

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the prior art as described above, in which a specific frequency within a band is used for a signal current to transmit a signal, and the specific frequency is received at a receiving side. A signal detection device for an in-band signal transmission device capable of reliably detecting the signal current without being disturbed by an external wave or the like in the in-band signal transmission device that separates the signal and reproduces the signal current Is intended to provide.

[0015]

According to the present invention, a first blocking circuit 4 for blocking the first signal f ₁ and the second signal f ₂ is provided.
A first signal detection circuit 6 for detecting the first signal f ₁ or the second signal f ₂ , an output of the first blocking circuit 4 and a first signal
Of the signal detection circuit 6 and the first comparison circuit 8 which generates an output by checking in terms of level and time. The second signal detecting circuit 7 for detecting a second blocking circuit 5 for blocking a third signal f ₃ and a fourth signal f _4, a third signal f ₃ or the fourth signal f ₄ And a second comparison circuit 9 which generates an output by checking the output of the second blocking circuit 5 and the output of the second signal detection circuit 7 in terms of level and time.

Further, there is provided a third comparison circuit 10 which generates an output by checking the output of the first comparison circuit 8 and the output of the second comparison circuit 9 in terms of level and time. Output of the second comparison circuit 8 and output of the second comparison circuit 9
A switching circuit 11 for selecting a signal form from the output of the comparison circuit 10 and a signal form according to the situation of the transmission line and the purpose of use to generate an output.

[0017]

The first blocking circuit 4 blocks the first signal f ₁ and the second signal f ₂ . The first signal detection circuit 6 detects the first signal f ₁ or the second signal f ₂ . The first comparison circuit 8 generates an output by checking the output of the first blocking circuit 4 and the output of the first signal detection circuit 6 in terms of level and time. That is, the first comparison circuit 8 generates an output when the first signal f ₁ or the second signal f ₂ is input.

The second blocking circuit 5 blocks the third signal f ₃ and the fourth signal f ₄ . The second signal detection circuit 7 detects the third signal f ₃ or the fourth signal f ₄ . The second comparison circuit 9 generates an output by checking the output of the second blocking circuit 5 and the output of the second signal detection circuit 7 in terms of level and time. That is, the second comparison circuit 9 generates an output when the third signal f ₃ or the fourth signal f ₄ is input.

The third comparison circuit 10 is the first comparison circuit 8
And the output of the second comparison circuit 9 are level-wise and temporally checked to generate an output. Switching circuit 11
Generates an output by selecting a signal form from the output of the first comparison circuit 8, the output of the second comparison circuit 9, and the output of the third comparison circuit 10 according to the situation of the transmission line and the purpose of use. To do.

Therefore, the switching circuit 11 receives one wave of the first signal f ₁ and the second signal f ₂ , or one wave of the third signal f ₃ and the fourth signal f _4. Since the output is generated only when they occur, or when they occur at the same time, it is possible to reliably prevent malfunction.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. First, in the embodiment shown in FIG. 1, the first blocking circuit 4 for blocking the first signal f ₁ and the second signal f ₂ is used.
And a first signal for detecting the first signal f ₁ or the second signal f ₂ .
Signal detection circuit 6 and a first comparison circuit 8 that generates an output by checking the output of the first blocking circuit 4 and the output of the first signal detection circuit 6 in terms of level and time. ing. The second signal detecting circuit 7 for detecting a second blocking circuit 5 for blocking a third signal f ₃ and a fourth signal f _4, a third signal f ₃ or the fourth signal f ₄ And a second comparison circuit 9 which generates an output by checking the output of the second blocking circuit 5 and the output of the second signal detection circuit 7 in terms of level and time. Further, a third comparison circuit 10 which generates an output by checking the output of the first comparison circuit 8 and the output of the second comparison circuit 9 in terms of level and time, and these first to third comparison circuits A switching circuit 11 is provided which selects the signal form from each output of the circuits 8 to 10 according to the situation of the transmission line and the purpose of use to generate an output. In addition, a first band pass filter 2 that passes a band including the first signal f ₁ and the second signal f ₂ is provided in front of the first blocking circuit 4 and the first signal detection circuit 6, and The third signal f is provided in the preceding stage of the second blocking circuit 5 and the second signal detection circuit 7.
_A second bandpass filter 3 is provided which passes a band containing ₃ and the fourth signal f ₄ . 12 is an interface circuit.

FIG. 2 shows a detailed configuration of the blocking circuit 4 in FIG. 1, in which a band-blocking filter 401 blocks the frequency f _{1 and} f ₂ components from the signal passed through the band-pass filter 2. Wave device, 402 is an amplifier, and 403 is a rectifier circuit.

FIG. 3 shows the signal current detection circuit 6 shown in FIG.
FIG. 5 shows a detailed configuration of a band-pass filter 501 for passing a frequency f ₁ component from a signal passed through the band-pass filter 2, and a reference numeral 504 for a signal passed through the band-pass filter 2. A bandpass filter that passes the frequency f ₂ component,
502 and 505 are amplifiers, 503 and 506 are rectifier circuits,
Reference numeral 507 is a comparator.

The blocking circuit 5 and the signal current detection circuit 7 in FIG. 1 also have the same structure as the blocking circuit 4 and the signal current detection circuit 6, but instead of the frequency f _{1 and} f ₂ components, respectively. , Frequency f _3, f ₄ components are blocked or passed.

The operation of the embodiment shown in FIG. 1 will be described below. The band pass filter 1 secures a band to be used and removes frequency components outside the band. The secured frequency band is divided by the band pass filters 2 and 3.

In the signal current detection circuit 6, the frequency f ₁
The component passes through the band pass filter 501, is amplified by the amplifier 502, and is converted into a direct current by the rectifier circuit 503 to generate the output indicated by the arrow. The frequency f ₂ component is the band pass filter 5
04, is amplified by the amplifier 505, and the rectification circuit 50
It is converted to a direct current at 6 to generate the output of the arrow. The comparator circuit 507 selects the higher level of both DC signals and generates the output of the arrow.

On the other hand, in the blocking circuit 4, the frequencies f _1, f
_{The two} components are blocked by the band stop filter 401, and the remaining frequency components are amplified by the amplifier 402 and converted into direct current by the rectifier circuit 403 to generate the output of the arrow.

The comparison circuit 8 compares the output of the blocking circuit 4 and the output of the signal current detection circuit 6 in terms of level and time to generate an output. That is, the comparison circuit 8 presets a level difference between the output level of the blocking circuit 4 indicating the band average value and the output level of the signal current detection circuit 6 indicating the level value of the frequency f ₁ or f ₂ , and the frequency f ₁ or by checking the pulse width of the output of the f _2, depending on the situation of the foreign wave or the like, and generates an output by detecting a signal of a frequency f ₁ or f _2.

FIG. 4 illustrates the operation of the comparison circuit 8. In the figure, the arrow indicates the output of the blocking circuit 4, and the arrow indicates the output of the signal current detection circuit 6, where the positive potential is 1 and the other than the positive potential is 0. The comparison circuit 8 compares the two outputs in terms of level and time to generate an output, but the output is 1 only when the frequency component f ₁ or f ₂ is normally received and becomes the output 1, and in other cases. Are all 0. The pulse width to be temporally compared is modified depending on the purpose of use.

The operations of the signal current detection circuit 7, the blocking circuit 5 and the comparison circuit 9 are similar, and the frequency component f ₃ or f
_The comparison circuit 9 generates an output which becomes 1 only when ₄ is normally received and becomes 0 in all other cases.

The comparison circuit 10 checks the outputs of the comparison circuits 8 and 9 in terms of level and time, and when only the comparison circuit 8 produces an output, it switches the switching circuit 11 to the side (a), The signal of the comparison circuit 8 is output, and the comparison circuit 9
When only the output is generated, the switching circuit 11 is switched to the (c) side to output the signal of the comparison circuit 9,
When the outputs of both comparison circuits 8 and 9 occur simultaneously, the switching circuit 11 is switched to the (b) side and the signal of the comparison circuit 10 is output.

As for the selection of the input signal in the switching circuit 11, a desired signal form can be selected according to the condition of the transmission line, the purpose of use, and the like. The signal from the output side c of the switching circuit 11 undergoes predetermined interface conversion in the interface circuit 12 and is output.

[0033]

As described above, according to the present invention, in a signal transmission device which uses a specific frequency within a band as a signal for a signal current, four specific frequencies within a band are used and the received signal is leveled. Since signal processing is performed by processing in time, signal detection can be reliably performed even in the presence of extraneous waves and interfering waves.

That is, according to the signal detection method for the in-band signal transmission device of the present invention, (1) the band pass filter 1 that allows only the frequency band to be used to pass is provided, so that the interference from the unused band is prevented. The influence of waves can be reduced.

(2) Since the signal current detection circuits 6 and 7 for detecting the specific 2 frequencies and the blocking circuits 4 and 5 for blocking the specific 2 frequencies are provided, (a) Interference that occurs instantaneously Not affected by the waves. (B) The presence of the blocking circuits 4 and 5 makes it possible to obtain the average value of the in-band components in real time. (C) Since the band pass filters 2 and 3 for separating the band including the specific two frequencies are provided, it is possible to perform high-accuracy high-speed signal transmission / reception with less malfunction.

(3) Since the output is selected according to the reception status of the specific signal within the band by including the switching circuit 11, the signal detection and the generation of the output that match the status of the transmission path and the purpose of use are generated. Can be done. (4) By using part of the comparison circuits 8 and 9 as a protection circuit, the level difference between the band average value determined by the level values of the blocking circuits 4 and 5 and f _1, f ₂ or f _3, f _4. Is set in advance and the level value and pulse width of f _1, f ₂ or f _3, f ₄ are checked, so that a real-time response is possible.

(5) Since the circuit structure is composed of a simple circuit having a similar block structure, it is easy to manufacture and maintain. (6) Since each filter, blocking circuit, detection circuit, and comparison circuit can be configured by digitization, the assembly work time can be shortened.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a detailed configuration of a blocking circuit 4 in FIG.

3 is a diagram showing a detailed configuration of a signal current detection circuit 6 in FIG.

FIG. 4 is a diagram illustrating an operation of a comparison circuit 8.

FIG. 5 is a diagram showing a conventional signal detection method in an in-band signal transmission device.

FIG. 6 is a diagram showing another conventional signal detection method in the in-band signal transmission device.

[Explanation of symbols]

 2 1st band pass filter 3 2nd band pass filter 4 1st stop circuit 5 2nd stop circuit 6 1st signal detection circuit 7 2nd signal detection circuit 8 1st comparison circuit 9 2nd Comparison circuit 10 Third comparison circuit 11 Switching circuit

Claims (2)

[Claims] 1. A first blocking circuit for blocking a _first signal f ₁ and a second signal f _2, and the first signal f ₁ or the second signal f 2.
A first signal detection circuit for detecting the signal f ₂ of
And a first comparison circuit that generates an output by checking in terms of level and time from the output of the blocking circuit and the output of the first signal detection circuit, and outputs the third signal f ₃ and the fourth signal. a second blocking circuit which prevents the f _4, and a second signal detection circuit for detecting a signal f ₄ of the third signal f ₃ or 4, output a second of said second blocking circuit A second comparison circuit that generates an output by checking the output of the signal detection circuit in terms of level and time, and outputs the output of the first comparison circuit and the output of the second comparison circuit in level. Third time checking and generating output
And a switching circuit for generating an output by selecting a signal form from the outputs of the first to third comparison circuits according to the situation of the transmission line and the purpose of use. Signal detection device for signal transmission device. 2. A first band pass filter for passing a band including the first signal f ₁ and the second signal f ₂ is provided in a stage preceding the first blocking circuit and the first signal detection circuit. And a second band pass filter for passing a band including the third signal f ₃ and the fourth signal f ₄ is provided in a stage preceding the second blocking circuit and the second signal detection circuit. The signal detection device for an in-band signal transmission device according to claim 1.