JPH01202094A - Dtmf signal detector - Google Patents

Abstract

PURPOSE:To reduce a sound error detecting rate by deciding the validity of a DTMF signal and outputting the signal only when the signal length of the received DTMF signal is longer than its effective signal length. CONSTITUTION:Effective signal lengths are stored in a storage circuit 8 in each operation mode of a device and in each DTMF signal, a DTMF signal detected by a DTMF signal detecting circuit 4 with the effective signal length by a comparator 9 and that only the DTMF signal having a signal length longer than the effective signal length is valid is decided and the signal is outputted. Thereby, the generation ratio of mulfunction due to sound can be reduced by setting the effective signals of the operation mode and the DTMF signal sort of the device which are easy to cause malfunction due to voice to a longer value.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a DTMF signal that is connected to a telephone line and is used in a voice mail device, a voice response device, etc. that is controlled by a DT signal sent from a telephone terminal or the like. Detection device (2 related)

BACKGROUND OF THE INVENTION FIG. 2 shows the configuration of a voice mail device using a conventional DTMF signal detection device. As shown in FIG. 2, the telephone line connection end 1 is connected to the hybrid circuit 2C.

The output terminal of hybrid circuit 2 into the device has an analog/
A digital conversion circuit 3 and a DTMF signal detection circuit 4 are connected. The output terminal of the DTMF signal detection circuit 4 is connected to the system control circuit 5. The output terminals of the analog/digital conversion circuit 3 and system control circuit 5 are connected to the storage circuit 6.
The output terminal of the storage circuit 6 is connected to the input terminal of the digital/analog conversion circuit 7. The output end of the digital/analog conversion circuit 7 is connected to the hybrid circuit 2.

Next, the operation of the above conventional example will be explained.

The voice signal and DTMF signal input from the telephone line connection end 1 pass through the hybrid circuit 2 to an analog/digital conversion circuit 3 and a DTMF signal detection circuit 4 (both are input by two people).
) When the TMF signal detection circuit 4 detects the DTMF signal,
The detected DTMI" signal type is output to the system control circuit 5. The system control circuit 5 controls the device according to the meaning of the DTMF signal type. For example, if the signal type received from the DTMF signal detection circuit 4 is If it means "recording", the system control circuit 5 stores the digitally encoded audio signal in the analog/digital conversion circuit 3 in the storage circuit 6. Conversely, if the signal type is
If it means "playback", the system control circuit 5 converts the audio signal stored in the storage circuit 6 into an analog signal in the digital/analog conversion circuit 7, and then transmits it from the telephone line connection end 1 through the hybrid circuit 2. Send to telephone line.

In this way, even with the conventional DTMF signal detection device, the device can be operated in response to the received DTMF signal.

Problems to be Solved by the Invention Since the DTMF signal is composed of a combination of two types of single frequency signals within the audio band, the DTMF signal detection circuit 4 may mistake the audio signal containing these frequency components as a DTMF signal. Easy to detect. However, when a conventional DTMF signal detection device detects a DTMF signal, it immediately determines that the DTMF signal is valid and outputs it regardless of the signal type. During transmission, the hybrid circuit 2 mistakenly detects the audio signal that bounces back into the device as a sidetone as a DTMF signal, and as a result, the device tends to malfunction.

The present invention solves these conventional problems, and provides a DT that can reduce the voice false detection rate.
The object of the present invention is to provide an MF signal detection device.

Means for Solving the Problems In order to achieve the above objects, the present invention provides a DTMF signal detection circuit that detects DTMF signal types and signal lengths, and stores effective signal lengths for each of a plurality of operation modes of the device and for each DTMF signal. and the above-mentioned DT in each operation mode.
The output of the MF signal detection circuit and the output of the effective signal length storage circuit are compared, and only when the signal length of the received DTMF signal is longer than the effective signal length as a result of the comparison, the DTMF signal is determined to be valid and output. It is equipped with a comparison circuit that performs the following steps.

Effects The present invention has the following effects due to the above configuration. That is, effective signal lengths are stored in a storage circuit for each operating mode of the device and for each DTMF signal, and a comparison circuit compares the DTMF signal detected by the DTMF signal detection circuit with the effective signal length, and detects a signal longer than the effective signal length. Only DTMF signals with a long length are determined to be valid and output. Therefore, in operating modes where erroneous detection due to audio (secondary detection) is likely to occur, such as the recording mode of a voice mail device, where audio signals are input for a long time while the DTMF signal is being monitored, Regarding the mode, an operation mode in which false detection due to voice is less likely to occur, such as a voice mail device, is more effective than a mode in which voice signals are not input/output and only DTMF signals are monitored. By setting the effective signal length long, the short time DT included in the audio signal can be
It is possible to reduce the possibility that the device will malfunction due to the MF signal component.

EXAMPLES Hereinafter, examples of the present invention will be described with reference to the drawings. FIG. 1 shows the configuration of a voice mail device using a DTMF signal detection device according to an embodiment of the present invention.

In this embodiment, the same parts as those in the conventional example will be described with the same reference numerals. As shown in FIG. 1, a telephone line connection end 1 is connected to a hybrid circuit 2. As shown in FIG. An analog/digital conversion circuit 3 and a DTMF signal detection circuit 4 are connected to the output terminal of the hybrid circuit 2 into the device. The output terminal of the DTMF signal detection circuit 4 is connected to the comparison circuit 9.
The comparison circuit 9 is also connected to the effective signal length storage circuit 8 and the system control circuit 5. The output end of the analog/digital conversion circuit 3 and the output end of the system control circuit 5 are connected to the input end of the storage circuit 6, and the output end of the storage circuit 6 is connected to the input end of the digital/analog conversion circuit 7. The output end of the digital/analog conversion circuit 7 is connected to the hybrid circuit 2.

Next, the operation of the above embodiment will be explained.

A voice signal and a DTMF signal inputted from the telephone line connection end 1 are inputted to an analog/digital conversion circuit 3 and a DTMF signal detection circuit 4 via a hybrid circuit 2. DT
When the MF signal detection circuit 4 detects the DTMF signal, it outputs the signal type and signal length to the comparison circuit 9. Comparison circuit 9
receives information about the operating mode of the device from the system control circuit 5 at all times. Further, the effective signal length storage circuit 8 stores effective signal lengths for each of a plurality of operation modes of the device and for each DTMF signal. Therefore, when the comparison circuit 9 receives the signal type and signal length from the DTMF signal detection circuit 4, it reads the effective signal length for the signal type in the operating mode of the device at that time from the effective signal length storage circuit 8, and detects the DTMF signal. Signal length received from circuit 4 and effective signal length storage circuit 8
Compare the effective signal length read from . As a result of the comparison, D
Only when the signal length of the TMF signal is longer than the effective signal length,
Comparison circuit 9 determines that the received DTMF signal is valid and outputs the signal type to system control circuit 5. The system control circuit 5 receives and receives signal types from the comparison circuit 9 and operates the device according to the meaning of the signal types. For example, if the signal type means "recording", the system control circuit 5 stores the audio signal digitally encoded by the analog/digital conversion circuit 3 in the storage circuit 6.

Furthermore, if the signal type means "playback", the system control circuit 5 returns the audio signal stored in the storage circuit 6 to an analog signal in the digital/analog conversion circuit 7, and then converts the audio signal stored in the storage circuit 6 back into an analog signal, and then converts the audio signal stored in the storage circuit 6 back into an analog signal. from the telephone line connection end 1 to the telephone line.

In this way, according to the above embodiment, an I
) Only when a TMF signal is detected, the DTMF signal is determined to be valid and output. Therefore, the incidence of malfunction of the device due to voice can be reduced by setting the effective signal length. For example, when monitoring a DTMF signal that means "end of recording" while an audio signal is being input, such as in recording mode, the DTM signal included in the audio signal
There is a high possibility that the device will malfunction due to the F signal component and end the recording, but by setting the effective signal length of the D'rMF signal, which means "end of recording" in the recording mode, to a longer value, the audio It is possible to reduce the incidence of malfunction due to

Effects of the Invention As described above, according to the present invention, the effective signal length is stored in the storage circuit for each operating mode of the device and for each DTMF signal, and the DTMF signal detected by the DTMF signal detection circuit is compared with the effective signal length. The circuit compares the signal length and determines that only the DTMF signal having a signal length longer than the effective signal length is valid and outputs it. Therefore, the operating mode of the device and DTMF, which are likely to cause malfunction due to voice,
By setting the valid signal to be long for the signal type, it is possible to reduce the incidence of malfunctions caused by voice.

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram showing a voice mail device using a DTiF signal detection device according to an embodiment of the present invention, and FIG. 2 is a schematic block diagram showing a voice mail device using a conventional DTMF signal detection device. . 1...Telephone line connection end, 2...Hybrid circuit, 3...Analog/digital conversion circuit, 4...D
TMF signal detection circuit, 5... system control circuit, 6.
...Storage circuit, 7.Digital/analog conversion circuit, 8.Valid signal length storage circuit, 9.Comparison circuit. Name of agent: Patent attorney Toshi Nakao (Male) 1st person
Figure 2

Claims (1)

[Claims] a DTMF signal detection circuit that detects the DTMF signal type and signal length; a storage circuit that stores effective signal lengths for each of the plurality of operation modes of the device and for each DTMF signal; and an output of the DTMF signal detection circuit and the effective signal in each operation mode The output of the long memory circuit is compared, and as a result of the comparison, the received DTM
A DTMF signal detection device comprising: a comparison circuit that determines a DTMF signal to be valid and outputs it only when the signal length of the F signal is longer than the effective signal length.