JPH01272368A - Dtmf receiver - Google Patents

Abstract

PURPOSE:To sense a service tone by means of a simple circuit constitution on one chip by using in common a clock generating circuit for driving a filter, a frequency converting means and a code converting means. CONSTITUTION:A service tone filter 10 for extracting only a service tone is connected to the output side of a low pass filter 2 and a zero crossing detecting circuit 7c for converting the output of the filter 10 into a pulse corresponding to its frequency is connected to the output side of the filter 10. A clock generating circuit 6 applies a clock signal similar to the one to be applied to a high group filter 4, a low group filter 5, a frequency detecting circuit 8, and a code converting circuit 9 to the filter 10. Receiving the clock, the filter 10 passes a service tone.

Description

[Detailed Description of the Invention] [Industrial Field of Application] This invention relates to a dual tone Mul of answering machines.
The present invention relates to a ti rrcquency (hereinafter abbreviated as rDTMFJ) receiver, and in particular to the sensing of DTMF signals and service tone signals from a switching center.

(Prior Art) FIG. 2 is a block diagram showing a conventional DTMF receiver that performs home security using an answering machine.

In the figure, reference numeral 1 denotes an input amplifier, to which a <DTMF signal based on a home security number or a service tone from an exchange center is input. Then, the input amplifier 1 amplifies and outputs the applied signal.

DTMF 1. A signal generally consists of a signal consisting of a combination of two frequency components, a relatively high frequency component and a relatively low frequency component. Hereinafter, a relatively high frequency component will be referred to as a high group frequency component, and a relatively low frequency component will be referred to as a low group frequency component.

The output signal of the input amplifier 1 is applied to a low-pass filter 2 for removing high frequency components such as noise contained in this output signal.

The output signal of the low-pass filter 2 is applied to a service tone removal filter 3 for removing service tones.

The output signal of the service tone removal filter 3 is high a\J3
and is input to low group filters 4 and 5.

The high group filter 4 passes only the high group frequency component of the DTMF signal, and the low group filter 5 passes only the low group frequency component of the DTMF signal H. High group filter 4. Both of the low group filters 5 are similar to the Swiss 4 Nyabashita filter.

High group noirta 4. The low group filter 5 is operated by the 1 cock signal from the clock generation circuit 6, and the high group nolter 4
．． The bandwidth of these filters is determined by the capacity h1 of the switched filter included in the low group filter 5 and the frequency of the clock signal.

1 group filter 4. The output signal of the low group filter 5 is input to the cross detection circuits 7a and 7b.The cross detection circuit 7a receives the high group frequency component from the high group filter 4,
The zero cross detection circuit 7b converts the low group frequency component from the low group filter 5 into a pulse 1. ′, convert and output.

The output pulses of the cross detection circuits 7a and 7b are given to the frequency detection circuit 8. The frequency detection circuit 8 receives the clock signal from the clock generation circuit 61), counts the number of pulses from the Urocross detection circuits 7a and 7b, and determines what the frequency components of the high and low groups are. do.

Therefore, the frequency detection circuit 8 determines which button of each button telephone was pressed based on the frequency combination of the n-group frequency component and the low-group frequency component, and sends the determination result to the code conversion circuit 9. Output.

The 21-code conversion circuit 9 receives the clock signals from the clock generation circuit 6 and converts the results determined by the frequency detection circuit 80 into binary numbers. The output of the code conversion circuit 9 is connected to a microcomputer or the like used in Baumseki Cority.

Next, the operation will be explained. After pressing the button corresponding to the telephone number and connecting the telephone line, the user enters the state of receiving a home security number. After that, press the button on the TCT phone corresponding to the predetermined number for performing home security. Then, a D1MF signal corresponding to the pressed number is generated 1 and given to the input amplifier 1. □This DT, MF signal is amplified by the input amplifier i&Z, and then passed through the low-pass filter 21. . 2, high frequency components such as noise are removed, and then passed through a service tone removal filter 3 to a high group filter 4. It is input to the low group filter 5.

The high snore filter 4 passes only the high frequency components of the DTMF signal! The low group filter 5 passes only the low group frequency component of the D'TMF signal and supplies it to the pyrocross detection circuit 7b.

I! 1] The misalignment detection circuits 7a and 7b each convert a high group frequency component and a low group frequency component into pulses corresponding to their frequencies. The frequency detection circuit 8
, 7b, detect the frequencies of the high group frequency component and the low group frequency component, and based on the combination, determine what kind of signal the D King MF signal is, and determine which button on the button telephone is pressed. Determine if it was pressed. Then, the code conversion circuit 9 converts the pressed number into a binary number L
·,Output. This output is input to a microcomputer (not shown), and home security is performed according to the number.

Next, the case where the telephone line changes from the open state to the disconnected state, that is, the case where the transmitting party hangs up the handset will be explained. In this case, no DTMF signal is input to the input amplifier 1, and only the service tone sent from the telephone exchange is input. , the number-tone is amplified by the input amplifier 1, high-frequency components such as miscellaneous noise are removed by the low-pass filter 2, and the frequency tone is removed by the service tone removal filter 3. In this case, high snoring filter 4. No signal is given to the low group filter 5. Here, the service tone removal filter 3 was provided by J.
x Due to the reason below. Generally, the frequency of the service tone is 4
00)-IZ, and the frequency of the low group frequency component of the DTM F signal is about 600 Hz.

Therefore, if the performance of the low group filter 5 is poor, the dial tone may also be passed. Then, the frequency detection circuit 8. If a signal other than the DTMF signal is input to the code conversion circuit 9, an erroneous output occurs, and home security cannot be performed normally. In order to prevent this, a service tone removal filter 3 is provided. In other words, the service tone removal filter 3 serves to assist the low group filter 5.

[Problem to be solved by the invention]

A conventional DTMF receiver is configured as described above, and the DTMF receiver itself does not have a function of sensing a beam tone. However, in the case of an answering machine, the answering machine itself disconnects the telephone line when the transmitting telephone is disconnected, so the telephone line is disconnected based on the service tone emitted from the exchange when the transmitting telephone is disconnected. A disconnect signal is created and the phone must have the ability to detect the service tone. Therefore, in the past, a separate chip was configured to sense the service tone. This poses a problem in that not only two chips must be provided, but also a clock generation circuit 6 and the like must be provided separately on the other chip.

The present invention was made to solve the above problems, and its object is to provide a DTMF receiver that can sense service tones on one chip and with a simple circuit configuration.

[Means to solve the problem]

an input means for receiving a DTMF signal and a service 1-- signal consisting of a combination of a plurality of frequency components; a first filter that receives the signal from the input means and separates and extracts each frequency component of the DTMF signal; a second receiving signal from the input means and extracting the service tone signal;
a filter, a frequency detection means for receiving the output of the first filter and detecting a combination of frequency components thereof, and operating the first filter, the frequency detection means, the code conversion means, and the second filter. The configuration includes a clock supplying circuit and a zero clock generation circuit.

[Effect]

The second filter in this invention is the first filter,
It operates by receiving the same clock as the frequency detection means and the code conversion means from the clock generation circuit, and passes only the service tone signal.

〔Example〕

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

In the figure, the difference from the conventional example shown in FIG. This is because a zero-cross detection circuit 7C that converts into pulses according to the frequency is newly provided. In this case, the clock generation circuit 6 uses the high group filter 4. A clock signal similar to that applied to the low group filter 51 frequency detection circuit 8 and the code conversion circuit 9 is applied to the service tone 10.

The service tone 10 is a switched capacitor filter, and its band is determined by the frequency of the six switched capacitors and the clock signal. The rest of the structure is the same as the conventional example shown in FIG.

Next, the operation will be explained. The case where the telephone line is connected, that is, the telephone line is connected, and then home security is performed is the same as in the conventional case.

In this case, since only the DTMF signal is input to the service tone filter 10, there is no output from the zero-cross detection circuit 7C. Therefore, no signal is created to disconnect the telephone line and the telephone line remains connected.

Thereafter, when the sender hangs up the telephone, a service tone is given to the receiver's telephone by the exchange. In this case, a service tone is input to the receiving telephone instead of the DTMF signal. This service tone is input to a service tone removal filter 3 and a service tone filter 10 via a low-pass filter 2. Since the service tone removal filter 3 removes the service tone, no signal is generated at the output of the service tone removal filter 3. Therefore, there is no output from the code conversion circuit 9, and home security may be performed incorrectly.
Group noirta 4. Low group f, gluta 51 frequency detection circuit t3
, 2"--Code conversion circuit 9 and the common D connection 6 pass the service tone. Are you looking forward to it? The iS range is as described above, where the stone filter 10 is configured as follows: f:1:21'', t, the capacity of the filter, and the frequency of the signal, t, J. , ri determined 8, zer]ri [1
The signal detection circuit 7c converts +j---jis] . A certain telephone on the receiving side is 3. ! ;Cut off line 4.

[Effects of the invention] L(7) J, sea urchin (2” invention 1c J-; tl
For example, a second filter for extracting the piston signal is provided, and a clock generation circuit for generating a signal for operating the second filter is connected to the first filter, frequency conversion means, =1-drive. A rounding clock generation circuit that operates the conversion f-stage and its use] ``When integrated into an integrated circuit, it is possible to sense Levistone with a one-chip circuit and a precise circuit configuration.Z>D' i-MF: The effect is that the i noceiver'5゜lJroL and r'' are made smaller.

46 Description of Drawings Figure 1 is a block diagram showing an embodiment of this 'Rill', and Figure 2 is a block diagram of a conventional DT' MF receiver in this issue.

Picture book: 4.4. j, high group filter/J, 5 is a low group filter, 6 is a SJ lock generation circuit, 8 is a frequency detection circuit, 9 &;t, :'I-do☆dust circuit, 10 IJ
It is a j+"-・Piston-5・-filter. In the f1 diagram, the - marks t, i, i, l are the same, and the parts corresponding to Gf are ']% i"n. Figure 2 Procedural amendment (voluntary) 1. Indication of the case Japanese Patent Application No. 1983-101711 Representative Moriya Shiki 5. “Detailed description of the invention column” of the specification to be amended 6. Contents of the amendment (1) Page 3 of the specification, lines 13 to 13 In line 14, "capacitance of switched capacitor included in filter 5" is corrected to "capacitance ratio of capacitor included in filter 5".

(2) "The band is the capacity of a switched key 1?pacita" on page 9, line 18 to line 19 of the specification,
Correct it to ``The band is the capacitance ratio of the capacitor included in the service tone 10.''

(3) In lines 6 and 7 of page 11 of the specification, "capacity of the switched main 11 vacitor" is corrected to "capacity ratio of the V vacitor".

2

Claims (1)

[Claims] (1) an input means for receiving a DTMF signal and a service tone signal consisting of a combination of a plurality of frequency components; a first filter that receives the signal from the input means and separates and extracts each frequency component of the DTMF signal; a second filter that receives a signal from the input means and extracts the service tone signal; a frequency detection means that receives the output of the first filter and detects a combination of its frequency components; the first filter, the frequency A DTMF receiver comprising a detection means, the code conversion means, and a clock generation circuit that supplies a clock for operating the second filter.