JPH0370241A - On-hook detector in telephone set - Google Patents

Abstract

PURPOSE:To prevent mis-detection of end of a call by sending an output representing the end of the call at an on-hook detection section when an output appears at a 1st band pass filter and no output appears at a 2nd band pass filter. CONSTITUTION:When a music including a signal component of 400Hz the same as a frequency of a busy tone is sent to a voice signal 101, a busy tone detection signal 13a goes to an H level and a voice detection signal 14a goes to an L level, and when a busy tone is sent to the voice signal 101, both the levels of the busy tone detection signal 13a and the voice detection signal 14a go to an H level. Moreover, when the voice signal 101 represents no voice, the busy tone detection signals 13a goes to an L level and the voice detection signal 14a goes to an H level. Thus, an output level of an AND gate G15 of the on- hook detection section 15 goes to an H level only when a busy tone is sent in the voice signal 101 to energize a transistor(TR) Q15. Thus, a current flows to a relay coil RL, a relay contact S15 is closed and the end of the call is indicated externally. Thus, mis-detection of the end of call is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a telephone that automatically responds to a call, and more particularly to a call end detection device for a telephone that detects the end of a call.

Unattended answering of calls received while you are away, using an answering machine that can remember the message, or a telephone that automatically receives broadcasts sent over a telephone line. Telephones are becoming increasingly popular. Telephones, which are becoming increasingly popular, need to respond unattended, so when the other party's call ends, it is necessary to detect the end of the call and disconnect the telephone from the public telephone line.

On the other hand, as the standard for public telephone lines, when the call ends, a 400H2 signal is sent out to the line intermittently at intervals of about 1 second, so the above telephone has the following characteristics: As shown in a, a call end detection device includes a bandpass filter 81 that passes the 40011Z signal, and a 400)1z detection unit 82 that detects whether the 400H2 signal appears in the output of the bandpass filter; Alternatively, as shown in Figure 3, there is a bandpass filter 83 that passes the 400H2 signal, and a period for detecting whether the intermittent period of the 400H2 signal appearing at the output of the bandpass filter 83 is 1 second. A call end detection device consisting of a detection section 84 is incorporated. The output 82a of the 400H2 detector 82 or the output 84a of the cycle detector 84 is used as a call end detection signal, and the telephone is disconnected from the public telephone line in accordance with the end call detection signal.

The contents of the calls sent to the above-mentioned automatic answering telephones are not limited to human voices; for example, messages sent from the head office to factories located in other prefectures far away from the head office. Equipment that connects audio signals from telephones installed in factories to public address equipment used for the purpose of simultaneous broadcasting uses an electrical signal to signal the start of the broadcast prior to the start of the broadcast. In many cases, music box sounds or music generated by the music box are played.

This music box sound or music, like the subsequent broadcast, is transmitted to the factory via public telephone lines, but if the music box sound or music contains the same frequency components as the busy sound, Because of this, a telephone that automatically picks up a call will react to the same frequency component as the busy tone included in the music box tone, etc., and even if it is just the music box tone being played. Regardless, 40
The 0■Z detection section 82 or the cycle detection section 84 may mistakenly detect that the call has ended, resulting in a problem that the telephone is disconnected from the public telephone line.

The present invention was conceived in order to solve the above problems, and its purpose is to provide a call end detection device for a telephone that can prevent false detection of call end.

In order to solve the above-mentioned problems in order to solve the above problem, the end-of-call detection device in a telephone according to the present invention includes a first bandpass filter that passes the busy sound, and a pass frequency of the first bandpass filter that is set to a frequency other than the busy sound. the second
a busy sound detection unit that sends out a busy sound detection signal when a busy sound is sent to the output of the first band pass filter; and an output level of the second band pass filter that is set in advance. A voice detection section that sends out a voice detection signal when a set level is exceeded, and a call-end detection section that sends out a call-end detection signal when a busy tone detection signal is sent and no voice detection signal is sent out. Adopt a configuration that has the necessary features.

The audio signal containing the same frequency component as the busy tone on the left is a signal containing the same frequency component as the busy tone and other frequency components, and the busy tone is a signal containing frequencies other than the busy tone. Since the signal does not contain any components, when an audio signal containing the same frequency component as the busy sound is derived, a busy sound detection signal and a voice detection signal are sent out, and the busy sound is derived. When this happens, only the busy tone detection signal is sent. Therefore, when the busy tone detection signal is sent out and the voice detection signal is not sent out, that is, when the busy tone is sent out, the end of call detection section sends out an end of call detection signal indicating that the call is over; In other cases, the end of call detection signal is not sent.

FIG. 1 is a circuit diagram showing electrical connections in an embodiment of the present invention.

In the figure, an audio signal 101 from a public telephone line is connected to one terminal of each of two capacitors C112, C113, and a resistor R113 via a capacitor C111 and a resistor R111, and the other terminal of the capacitor C112 is OP. The other terminal of the resistor R113 is connected to the output of the amplifier OpH, the other terminal of the resistor R113 is connected to the reference voltage ref, and that of the capacitor C113 is connected to the negative input of the OP amplifier 0PII. Further, a resistor R112 is connected between the negative power and the output of the OP amplifier QPL1, and a reference voltage ref is applied to the positive power.

The output of the P amplifier 0PII is led to one input of a phase comparator 131 via a capacitor C131, and the output of the phase comparator 131 is led to an input of a loop filter 132. The output of this loop filter 132 is connected to the control power of a voltage controlled oscillator 133, and the output of the voltage controlled oscillator 133 is given to the other input of the phase comparator 131.

Three capacitors C121 to C123 and three resistors R1
Consisting of 21 to R123 and OP amplifier 0P12,
a second bandpass filter 1 into which the audio signal 101 is guided;
2 has the same connection as the first bandpass filter 11 consisting of three capacitors C111 to C113, three resistors R11l to R113, and ○P amplifier 0P11, and only the values of the elements are different. A detailed explanation will be omitted.

The output of this second bandpass filter 12 is connected to the cathode of a diode 0141 whose anode is grounded, and the anode of a diode D142 via a capacitor C141 and a resistor R141. It is grounded via C142 and connected to one terminal of resistor R142. Further, the other terminal of the resistor R142 is connected to the resistor R1
It is grounded via 43 and connected to the base of transistor 14, and the emitter of transistor 14 is grounded. The collector of the transistor 14 is connected to the positive power supply P via a resistor R144, and the output sent from this collector is guided to one side of the AND gate GI5 as a voice detection signal 14a.

A lock output sent from the phase comparator 131 and indicating that the phase is locked is output as the busy sound detection signal 13a.
The output of the AND gate G15 is connected to one terminal of the resistor R151. The other terminal of the resistor RI51 is grounded via a resistor R152 and connected to the base of the transistor 15. Further, the emitter of the transistor 15 is grounded, and the collector is connected to the anode of the diode 015 and one terminal of the relay coil RL.

And the other terminal of relay coil RL and diode 01
The cathode of No. 5 is connected to a positive power source P, and the contact output of the relay contact S15 corresponding to the relay coil RL is sent to the outside as a call end detection signal 15a.

In the above configuration, the busy sound detection unit 13 includes three blocks: a phase comparator 131, a loop filter 132, and a voltage controlled oscillator 133, and the audio detection unit 14 includes two capacitors C141 and C142. ，
4 resistors R141 to R144, 2 diodes 01
41, 0142, and a transistor 14. Further, the end of call detection section 15 detects the relay coil R.
It consists of L, relay contact S15, AND gate G15, two resistors R151 and R152, diode 015, and transistor 15.

The operation of one embodiment of the present invention having the above configuration will be described below.

The first band pass filter 11 has a busy tone of 400 kHz.
Since the values of each element are determined so as to operate as an active bandpass filter that passes the H2 signal, the output of the first bandpass filter 11 includes a busy signal indicating that the other party's phone is disconnected. A signal of 400H7, which is a sound, or a signal component around 400H2 included in music transmitted from the other party appears.

The busy sound detection unit I3 to which the output of the first bandpass filter 11 is guided forms a phase-locked loop circuit consisting of a phase comparator 131, a loop filter 132, and a voltage-controlled oscillator 133. When a signal in the capture range near 400H2 appears at the output of the first bandpass filter 11, the oscillation frequency of the voltage controlled oscillator 133 is made to follow the frequency of this signal, and its phase is made to follow the frequency of this signal. When the phases of both the output of the bandpass filter 11 of No. 1 and the output of the voltage controlled oscillator 133 match, it is assumed that a busy tone has been detected.
The level is output to the busy sound detection signal 13a. In other words, the busy sound detection signal 13a is generated not only when a busy sound is transmitted, but also when music or the like is transmitted as the audio signal 101, and the music is
Similarly, when the signal component of 00H2 is included, the signal becomes H level.

Next, the operation of the second bandpass filter 12 will be explained.

The signal band that can be used on the telephone is 300H2~3
．． The band is 4KHz, and audio signals such as speech are
Generally, the intensity distribution tends to be high near 8008Z. On the other hand, the signal of 40011Z, which is the busy tone, is not an ideal sine wave with a single frequency, so there are harmonics of integral multiples, and the higher the multiple, the smaller the harmonics. The bandpass filter 12 is configured to pass a band from 1KH2 to 2KHz, which is a frequency that is not easily affected by harmonics and causes little decrease in the signal strength of the audio signal.

The audio detection unit 14 to which the output of the second bandpass filter 12 is guided includes a capacitor C141 and a resistor R1.
The audio signal guided through 41 is connected to two diodes 0
141, R142, smoothed by capacitor C142, and applied to the base of transistor 14 via resistor R142, rectified by diodes 0141, D142, and divided by resistors 11142, R143. When the applied base voltage exceeds approximately 0.7V, transistor 1
The collector and emitter of No. 4 are electrically connected, and the collector level becomes L level. In other words, the audio detection signal 14a, which is the output of the audio detection section 14, goes to the L level when music, speech, or the like is sent to the audio signal 101.

From the above, when music containing the same signal component of 400H2 as the busy tone is sent to the audio signal 101, the busy tone detection signal 13a becomes H level, the voice detection signal 14a becomes L level, and the busy tone is sent to the audio signal 1°1, the busy tone detection signal 13a and the audio detection signal 14a
Both levels become H level. Also, the audio signal 101
When indicates silence, the busy sound detection signal 13a becomes L level and the voice detection signal 14a becomes H level. Therefore,
The output level of the AND gate G15 of the end of call detection section 15 is:
Only when the busy tone is sent to the audio signal 101, it becomes H level and makes the transistor Q15 conductive.
Current flows through the relay coil RL, closing the relay contact S15, and indicating to the outside that the call is over.

Note that the present invention is not limited to the above embodiment, and as shown in FIG. AGC circuits 21.2 and 14 respectively.
2, the level of the audio signal 101 can be reduced due to the length of the distance between the telephones, or even when the distance between the telephones is constant. In response to a decrease in the level of the audio signal 101 caused by the level at the time of transmission from the other party, the AGC circuit 21.22 corrects the decrease in the level, and the signal is guided to the two detection units 13.14. By always keeping the level constant, it is possible to achieve a configuration in which the detection operation is performed more reliably.

Further, as shown in FIG. 2, the audio signal 101 is converted into A(1
, C circuit 23 to the first and second bandpass filters 11.12, the AGC
By using only one circuit, it is possible to create a configuration that performs the same operation as the configuration shown in FIG. 2a.

Further, regarding the busy sound detection signal 13a, 4 is the busy sound.
We have described the case where the level is detected to determine whether or not the 00H2 signal is being sent out. When the signal is within a specified range, a signal indicating that a busy tone has been detected may be sent to the outside.

Regarding the audio detection unit 14, although the configuration in which the level is detected by the transistor 14 has been described, it is also possible to adopt a configuration in which the level is detected by a comparator to which a reference voltage is applied to one of the human inputs. be.

Furthermore, regarding the second bandpass filter 12, a case has been described in which a configuration is adopted in which a band from IKIIZ to 2KH2 is passed as a frequency other than the busy sound. 1.
It is possible to have a configuration in which a band such as 5KH2 is passed.

Furthermore, regarding the end of call detection section 15, a case has been described in which the contact output of the relay contact 515 is used as the end of call detection signal 15a. However, other output methods, such as A
(ND game) It is possible to use a configuration in which the output of G15 is used as a call end detection signal.

An end-of-call detection device for a telephone according to the present invention includes a first bandpass filter that passes a busy sound and a second bandpass filter that passes frequencies other than the busy sound,
When an output appears in the first bandpass filter and no output appears in the second bandpass filter, the end of call detection section sends out an output indicating the end of the call, so the same frequency as the busy sound is generated. When a signal including a component is led, an output indicating the end of a call is no longer sent out, so that it is possible to prevent erroneous detection of the end of a call.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an electrical connection of an embodiment of the present invention, FIG. 2a is a block diagram schematically showing a second embodiment of the present invention, and FIG. FIGS. 3A and 3B are block diagrams illustrating the electrical configuration of the conventional technology. 11... First band pass filter 12... Second band pass filter 13... Busy sound detection section 13a... Busy sound detection signal 14... Voice detection section 14a... Voice Detection signal 15... End of call detection section 15a... End of call detection signal

Claims (1)

[Claims] (1) A first bandpass filter that passes the busy sound, and a second bandpass filter whose passing frequency is set to a frequency other than the busy sound.
a busy sound detection unit that sends out a busy sound detection signal when a busy sound is sent to the output of the first band pass filter; and an output level of the second band pass filter that is set in advance. a voice detection section that sends out a voice detection signal when a set level is exceeded; and a call-end detection section that sends out a call-end detection signal when the busy tone detection signal is sent out and the voice detection signal is not sent out. An end-of-call detection device for a telephone, characterized by comprising: