JPS6167357A - Hand free telephone set - Google Patents

Abstract

PURPOSE:To improve the hand free talking by utilizing that a talker utters with sound volume more than a noise level so as to distinguish the voice from the noise. CONSTITUTION:When a reception signal is outputted from a hybrid circuit 5 and passes through a broad band-pass filter 14, a signal at an audible band only is outputted. The signal is averaged for several seconds by a level averaging circuit 16 and the result is given to a level comparator 17 as a noise level of the line. The level is compared with an output of a voice band filter and when the voice band output is larger, an output signal is fed to a level comparator 9 and compared with a surrounding noise level of a level comparator 21. Since the noise is distinguished from the voice in this way, a hand free telephone set is used in an excellent way with a telephone line having much noise or in a room having a large surrounding noise.

Description

[Detailed Description of the Invention] Industrial Field of Use The present invention relates to a telephone device that allows telephone calls to be made using a speaker and a microphone mounted inside the telephone without using a handset. It is.

Configuration of conventional example and its problems Figure 1 shows a conventional hands-free telephone device.
is connected to telephone line 2 by a hands-free circuit. 3
is a switch, and this switch 3 selects between a Ndocenote call and a Ndofuli call. That is, the terminal I is the side for hands-free communication and is connected to the handset communication circuit 4, and the terminal 2 is the side for hands-free communication.

Reference numeral 5 denotes a hybrid circuit, which separates reception and transmission.

The output of this hybrid circuit is connected to an analog switch 6. The output of analog switch 6 is connected to receiver amplifier 7.
The signal is amplified and output from the speaker 8. Further, the transmitted voice enters the transmitting voice amplifier 12 from the microphone 11, passes through the analog switch 13, and is connected to the hybrid circuit 6. 9 is receiving the call.

It is a level comparator for transmitting speech, and compares the receiving output of the hybrid circuit 5 and the transmitting output of the microphone 11, and outputs the result to the analog switch 6 and the inverter 10. The inverter 10 inverts the output of the level comparator 9 and outputs it to the gate of the analog switch 13.

Next, the operation of the above conventional example will be explained. In FIG. 1, when the level comparator 90 inputs, when the transmitting output of the microphone 11 is larger than the receiving output, the transmitting state is established, and the analog switch 13 is turned ON by the level comparator 9.
, a signal that turns off the analog switch 6 is output. In addition, if the output of the microphone 11 is smaller than the output of the microphone 11, the level comparator 9 receives a signal that turns the analog switch 13 OFF and the analog switch 6 ON. It is output from

However, in the above-mentioned conventional example, only the levels of receiving and transmitting calls are compared, so if you use a hands-free phone in a place with a lot of ambient noise, if the input from the telephone line is small, you will always be stuck in the transmitting state. There was a drawback. On the other hand, if there was a lot of noise on the telephone line, there was also the drawback that the phone was always on the receiving end.

OBJECTS OF THE INVENTION The present invention eliminates the above-mentioned conventional problems, and aims to enable excellent hands-free calls even in a room with a lot of ambient noise or on a noisy telephone line.

Structure of the Invention In order to achieve the above object, the present invention provides a level averaging circuit that averages telephone line noise and room noise for a certain period of time, a voice band filter that selects a voice band frequency, and an output of these level averaging circuits. This device is equipped with a level comparator that compares the output of the voice band filter and a level comparator that compares the output of these two level comparators and switches between the transmitting circuit and the receiving circuit. This improves free calls or hands-free calls on noisy telephone lines.

DESCRIPTION OF EMBODIMENTS The present invention will be described below with reference to FIG. 2, which shows one embodiment thereof. In Fig. 2, 1 is a hard/free circuit, 2 is a telephone line, 3 is a switch, 4 is a handset communication circuit, 5 is a hybrid circuit, 6 is an analog switch, 7 is a receiving amplifier, 8 is a speaker, and 9 is a A level comparator, 10 is an inverter, 11 is a microphone, 12 is a transmitting amplifier, and 13 is an analog switch, which are the same as the conventional one shown in FIG. Reference numerals 22 and 23 are additional circuits, and 14 is a wide band pass filter, which selects a signal of several tens of Hz to 10 KHz from the output of the hybrid 5.

This output is connected to an audio band filter 15 and a level averaging circuit 16 for several seconds. The output of the level averaging circuit 16 is connected to a level comparator 17 for comparison with the output of the audio band filter 16. The output of level comparator 17 is connected to level comparator 9. 18 is a wide band pass filter, 19 is an audio band filter, 2o is a level averaging circuit, and 21 is a level comparator.

Next, the operation of the above embodiment will be explained. - In FIG. 2, a reception signal is output from the hybrid circuit 5.

This received signal includes telephone line noise and voice. The received signal first passes through a broadband Bandhus filter 14, and a signal only in the audible band is output. Level average circuit 1
6 averages this output signal for several seconds and transmits it to the level comparator 17 as the line noise level. The voice band filter 15 has a voice band frequency of 300 Hz used in telephones.
~3.4KHz is selected and output. Level comparator 1
7 compares the output levels of the audio band filter 15 and the level averaging circuit, and sends an output signal to the level comparator 9 if the audio band output is larger than the average value output. If the audio band output is smaller than the average output, no signal is sent. Similarly, on the transmitting side, only the audible band is selected from the signal input from the microphone 11 using the broadband bandpass filter 18.
The level averaging circuit 20 averages the signal for several seconds and uses it as the ambient noise level of the room. In addition, a wideband bandpass filter 18
An audio band filter 19 selects only the frequencies used by the telephone, and sends the output to a level comparator 21. The level comparator 21 compares the ambient noise level (output of the level averaging circuit 20) and the output level of the audio band filter 19,
If the output of the audio band filter 19 is higher than the ambient noise level, a signal is sent to the level comparator 9. Furthermore, if the output of the audio band filter 19 is smaller than the ambient noise level, no signal is sent to the level comparator 9. As a result, the level determination for receiving and transmitting is as follows.

[Reception level] Only when a signal that is louder than the line noise is received, that signal is treated as a reception signal.

[Talking level] Only when a sound louder than the surrounding noise is received, that sound is treated as a transmitting signal.

This takes advantage of the fact that ambient noise or line noise is usually at a certain level in a given room or line, and that callers always speak at a volume above the noise level.
It distinguishes between noise and voice. (If you speak below the noise level, your voice will be masked by the noise and no one will be able to hear it.) This distinction between noise and voice allows you to speak on a noisy phone line or in a room with a lot of ambient noise. of··
This makes it possible to use a handset free telephone.

Effects of the Invention As is clear from the above embodiments, the hands-free telephone device of the present invention provides the following effects.

(-) Since the noise level of the telephone line and voice are distinguished, the hands-free telephone does not always remain on the receiving end and cannot send a call on a noisy telephone line.

(b) Since the ambient noise in the room and the transmitted voice are distinguished, even in a room with a lot of ambient noise, the hands-free telephone does not always remain in the transmitting mode and cannot receive calls.

[Brief explanation of the drawing]

Figure 1 is a block diagram of a conventional free telephone device.
FIG. 2 is a block diagram of a hands-free telephone device showing one embodiment of the present invention. 1...hand-free circuit, 2...telephone line, 3...switch, 6.13...analog switch, 8...speaker, 9,17.21... Level comparator, 10... Inverter, 11...
...Microphone, 14.18...Wide band pass filter, 15.19...Audio band filter, 16.20.Level averaging circuit.

Claims (1)

[Claims] A level averaging circuit that averages noise over a certain period of time, a voice band filter that selects a voice band frequency for outgoing calls, a level comparator that compares the level of the level average circuit and the output of the voice band filter, and a level comparator that compares the level of the level average circuit and the output of the voice band filter, A level averaging circuit that averages over a certain period of time, a voice band filter that selects the voice band frequency of the received call, a level comparator that compares the outputs of this level average circuit and the voice band filter, and a comparison of the outputs of the two level comparators. A hands-free telephone device equipped with a level comparator that switches between a transmitting circuit and a receiving circuit.