JPS6248162A - Hand-free telephone set - Google Patents

Abstract

PURPOSE:To decrease the unnaturality of conversation by designing a hand-free circuit so as to adopt a variable binary corresponding to a transmission mode and a reception mode for the gain of a transmission signal amplifier and a reception signal amplifier and the gain of a transmission level amplifier and a reception level amplifier. CONSTITUTION:A transmission signal is inputted to the transmission level amplifier 11 as it is through a terminal 1b of an analog switch 8 when the transmission has priority, while a reception signal is inputted to a reception level amplifier 12 through a terminal 2c and the attenuator ATT-12, and in case of VR>VT when the reception has priority, the transmission signal is inputted to the transmission level amplifier 11 through the attenuator ATT-11 conversely, while the reception signal is inputted to the reception level amplifier 12 without being attenuated through a terminal 2b. That is, the inconvenience that the path connected with priority during a conversation is changed over because of a sound or noise in the opposite path or an agreeable response of an opposite party when the path with priority has small voice is avoided. Thus, natural conversation is maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application J] This invention relates to a loudspeaker telephone (hereinafter referred to as a hands-free telephone) used in a car-mounted self-help telephone.

[Prior art J] Using a car phone while driving a car is undesirable in terms of steering wheel operation and safety, so a hands-free phone is useful as a means of making calls without using a handset. It is.

FIG. 3 is a block diagram of a conventional car phone with a hands-free phone. In this figure, (1) is an antenna that transmits or receives radio waves, (2) is a transmitter (21), a communication device (
22), the radio device (3) sends the audio input from the external microphone (4) as a modulated signal to the f-key section of the transmitter of the radio device (2), or receives the signal from the radio device (2). This is a hands-free telephone that obtains demodulated output from the demodulator of the device, amplifies the signal, and sends it to the speaker (5). The hands-free telephone (3) is equipped with a microphone amplifier (6) that amplifies the minute output of the external microphone (4), and a transmitting signal amplifier (7) that amplifies the output to an appropriate modulation signal output level. , terminals (la) and (lb) of the analog switch (8) are connected between the output of the microphone amplifier (6) and the input of the amplifier (7).
are connected to each. The truth (9) is the radio (2)
) is a receive signal amplifier that inputs and amplifies the demodulated output signal from the analog switch (8), and its output is connected to the terminal (2a) of the analog switch (8), and then sent to the power amplifier (
10). The output of the power amplifier (10) is driving the speaker (5). Also, the output of the microphone amplifier (6) is connected to the input of the transmit level amplifier (11).

Its output is a capacitor (C1), a diode (Di),
It is connected to the positive input terminal of the voltage ratio converter (13) through a series plate of a resistor (R1), and a parallel plate of a 1IIJK resistor (R2) and a capacitor (C3) to the ground is connected to the positive input terminal. is connected. Similarly, the output of the receive signal amplifier (9) is connected to the input of the receive level amplifier (12), and its output is connected to the capacitor (C2), diode (D2),
It is connected to the negative input terminal of the voltage ratio converter (13) through a series plate of a resistor (R3), and a parallel resistor (R4) and capacitor (C4) are connected between this negative input terminal and the ground. The plates are connected A.

The output of the voltage comparator (13) is connected to the control terminal of the analog switch (8). The external microphone (4) and speaker (5) are placed at an appropriate distance.

Next, the operation will be explained. The radio device (3) is a simultaneous transmitting and receiving method (duplex method) radio device. The output of the external microphone (4) is amplified by a microphone amplifier (6) and then further amplified by a transmitting level amplifier (11) K. This output passes through a DC cant capacitor (C1) and a diode (DI
)K, (R1) (R2) , (C3)
becomes a DC voltage VT in the smoothing circuit. On the other hand, the received demodulated signal is amplified by a receiver number amplifier (9), and then further amplified by a receiver level amplifier (12). This output passes through a DC cant capacitor (C2) e and a diode (D
2), it becomes a DC voltage VR through a smoothing circuit of n (R3) (R4) (C4). The above vT and this VR level are compared by a voltage comparator (13), and VT
> v, , the output of the ri voltage comparator (13) is 1”t
High 'H', conversely Low when VT < VR
'L'.And when it is VT and VR, it becomes 'L'.
It is assumed that the terminal (1a) of the log switch (8) is connected to (1b) and controlled to (2a) 11 (2d). Similarly, when T<VR, terminal (1a) is connected to (lc) and terminal (2a) is controlled to (2b).

The gains of the microphone amplifier (6) and the transmitting signal amplifier (7) are adjusted so that the modulation frequency deviation becomes the same as that of the standard voice input to the external microphone (4) of the speaker. Excerpt,
At that time, the amplifier of the transmitting level amplifier (11) is determined to be at a level VT=v8 at which the voltage comparator (13) sufficiently operates, and the receiving signal amplifier (9),
The gain of the power amplifier (10) is adjusted so that the standard demodulation level for the received Keyakifu-hen A-variant becomes the optimal speaker output sound pressure, and the gain of the receiving level amplifier (12) is determined so that German = V8. It is assumed that Therefore,
When transmitting and receiving from the other party's side at the same time, when the transmitting level is higher than the receiving level (VT > VR), the audio to the external microphone (4) is transmitted to the external microphone (4). (2) reaches the transmitter, and the voice from the receiver does not come out of the speaker.

Similarly, when the receiving level is higher than the sending level, Va > v
At T, the receiving sound from the receiver is output from the speaker, but the transmitting sound is not sent out as a modulated output because the transmission path is cut off by the analog switch and does not reach the transmitter.

In this way, the transmitting level and the receiving level Vi are constantly compared by the voltage comparator (13), and the output controls the analog switch (8), so that only the louder sound is transmitted to the other party. This means that when the sound output from the speaker enters the microphone, the sound is transmitted to the other party, and the other party sends it out to become the received sound, the noise is suppressed.

The rise time of vT or vR input to the voltage comparator (13) is approximately RIXC3 (seconds) and R3XC4 (seconds), respectively.
8 seconds), and vice versa, the rise time is determined by R2XC5 (
O general VC determined by R4XC4 (seconds), R4XC4 (seconds)
R1 (R2, +3 (R4) is set. Also, the rising time is set as ioo~5, taking into account the pause time of the voice during the conversation.
00m5K is selected.

[Problems to be solved by the invention] Conventional hands-free circuits are configured as described above, but when the call is being made, the other party's voice, such as greetings, cannot be heard, and when the call is being received, the caller's voice cannot be heard. is not transmitted to the other party at all, there is a slight rise time before the analog switch (8) switches on, and the beginning of the conversation is cut off, and even while transmitting, noises and other sounds from the other party momentarily become louder than the transmitted voice. As the child grows older, the child easily switches to listening, and as with the previous case, the conversation tends to be cut off in the middle, making the conversation unnatural.

The present invention has been made in order to solve the above-mentioned problems, and is a hands-free circuit that can reduce the unnaturalness of conversations by preventing conversation from breaking down and allowing two-way conversation to a certain extent. The whole purpose is to excel.

[Means for Solving the Problems] The hands-free circuit according to the present invention controls the gain of the transmitting signal amplifier (7) and the receiving signal amplifier (9) following the analog switch, as well as the transmitting level amplifier (11) and the receiving signal amplifier. The gain of the level amplifier (12) is set to a binary OT variable corresponding to each of the transmit mode and the receive mode.

[Function] That is, in the hands-free circuit according to the present invention, when the transmitting sound is louder than the receiving sound, the gain of the transmitting signal amplifier (7) and the transmitting level amplifier (11) is increased, and the gain of the receiving signal amplifier (9) is increased.
Since the gain of the receiving level amplifier (12) is made small and vice versa when the receiving signal is larger, it is possible for both the transmitter and the receiver to talk at the same time, and howling can be reduced. There is no interruption at the beginning of a conversation, and the switching system has hysteresis characteristics, so it is resistant to disturbances such as noise.

In Figure 1, (1) to (13), (la) (lb) (
lc) , (2a) (2b) (2c), (C1)~
(C4), (DI) (D2), (R1)~(
R4) is the same as or equivalent to that shown in FIG.

However, the transmitting signal quadrupler (7), the power amplifier (10), the transmitting level amplifier (11), and the receiving level amplifier (12) have two cell input terminals, that is, an attenuator (ATT).
i (1 = 7, 10, 11, 12), and the following input terminal and 1+: are equipped with a terminal without a line, and are designed so that the amplifier gain can be increased by selecting all of them. .

Next, the operation will be explained. The voice of the caller is input to the external microphone (4), and its output is amplified by the microphone amplifier (6)! ``After L, the analog switch (8) terminal (la
)to go into. The voice of the other party is demodulated by the receiver of the Vi wireless device (3), amplified by the receive signal amplifier (9), and then input to the terminal (2a) of the analog switch (8).

The analog switch is controlled by the output of the voltage ratio softener (13), and its predecessor is the conventional one mentioned above, l!
-f does not change. In other words, when VT > VR, (1a)
The terminal is connected to the (1b) terminal, the (2a) terminal is connected to the (2c) terminal, and vice versa when VR>VT, the (1a) terminal is connected to the (lc) terminal, and the (2a) terminal is connected to the (2b) terminal. Connected to the terminal. If VT>VR, where the legitimate speaker's voice is stronger than the received voice, the transmitting signal is directly input to the transmitting signal amplifier (7), amplified, and then modulated by the transmitter and sent out. On the other hand, the received signal amplifier (9) passes through an attenuator ATT-10, enters the power amplifier (10), and after amplification is output as a received signal from the speaker (10). Speakers (5) and external microphones (4)
The speakers (5) are placed as far away from each other as possible so that the sound received from the speaker (5) does not enter the external microphone (4).
In order to prevent the spatial loss between the speakers (5) and the microphone (4), a certain amount of the received sound from the speaker (5) must enter the microphone (4).

This relationship is the same on the other party's side, and the value of the attenuation amount of the ATT-10 is determined so that the gain of the closed loop formed between the self-help vehicle telephone side and the other party's side becomes 1 or more and does not cause hackling.

By the way, if the value of the attenuation amount of ATT -10 is appropriate, even when VT>VR, the speaker can hear the receiving volume as a certain level. The amount of attenuation of the ATT-10 that allows the speaker to understand the receiving volume sufficiently and does not cause no-cling, that is, the gain from the analog switch (2b) terminal to the output of the power amplifier (10) and the i-signal (2c) The optimal gain difference from the output of the power amplifier (10) to the output of the power amplifier (10) is 10 to 20 dB. This is because the general receiving sound is 80dB8p.

On the other hand, the noise inside the car is 70dB8p when driving at high speed.
. Therefore, the standard input sound pressure sensitivity of the external microphone (4) to the voice transmitted is 70 dBsp, which is the limit that can be distinguished from the noise level. Or if it has to be more than that, and if the distance between the speaker (5) and the external microphone (4) is approximately the same, then 80dB8pc and 70dB.
It is necessary to compensate for the attenuation of dBspc, that is, 10 dB or more, 1 ATT - 10, but on the other hand, the difference between the standard listening volume and the volume that can be noticed when the receiving sound is attenuated. This is because the limit is about 20 dB.

In the case of vR > vT, where the receiving sound is louder, the attenuation amount of ATT-7 is set to lO ~ 20 in the same way as the value of ATT-10, so that the transmitting sound from this side can be heard.
dB.

By the way, when priority is given to transmitting, that is, when VT > VR, the transmitting signal 4j l't analog switch (8) terminal (
1b) and goes directly to the transmit level amplifier (11).
The signal is input to the receiving level amplifier (12) through the attenuator ATT-12, and vice versa, if the receiving priority is VR>V-r, the transmitting signal passes through the attenuator ATT-11 and is input to the transmitting level amplifier (12). (11), while the receive signal is input to terminal (2b
) without attenuation through the receive level amplifier (12)
is input.

In other words, the route that is connected preferentially during conversation (the sending line or the receiving line) is the opposite route (the receiving line or the sending line).
This eliminates problems such as noises or noise, or switching systems due to the other party's voice when the voice of the priority system becomes low. This is because in order for the analog switch to change depending on the sound or voice on the opposite side of the system that is connected with priority, the voice must be louder by the attenuation amount of the attenuator LTT-12 (in the opposite case, ATT-il). Or because it is impossible to make a sound. In other words, it has sterile properties that give it a sharp aroma. This decay ii is usually selected to be 15 to 2 dBK to sufficiently compensate for the amount of intonation in the voice.

The operation of the other parts of the hands-free telephone according to the present invention is equivalent to the conventional embodiment.

Further, in the above embodiments, (7), (9), (10), (
An attenuator is connected to one of the nine input terminals of 11), but if the attenuation of ATT-7 is equal to the attenuation of ATT-11 and the attenuation of ATT-10 is equal to ATT-12, the transmission is Gain of speech level amplifier (11) The gain of the speech level amplifier (11) is not changed to 9, but is constant, and the input of the transmitting speech level amplifier and the output of the transmitting speech level amplifier are connected, and the input of the receiving speech level amplifier (12) is connected. There is also a female embodiment as shown in FIG. 3 which is connected to the output of a force multiplier (lO).

[Effects of the Invention] As described above, according to the present invention, since an audio signal is also output from the other party's system which is operating preferentially, it is possible to always check the other party's conversation, and of course there is no interruption at the beginning of a word. The switching system has hysteresis characteristics even in response to voice intonation and noise during conversation, allowing natural conversation to be maintained without being interrupted or accidentally switched.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a hands-free telephone according to an embodiment of the present invention, Fig. 2 is a block diagram showing an embodiment of the present invention, and Fig. 3 shows a conventional hands-free telephone. It is a block. (1) is the antenna, (2) (/'i radio, (3) is the hands-free phone, (4) is the external microphone, (5) is the speaker, (6) is the microphone amplifier, (7) is Transmitting signal amplifier, (8) is analog switch, (9) is receiving signal 8 increase 1
(10) is a power amplifier, (11) is a transmitting level amplifier, (12) is a receiving level amplifier, (13) is a voltage comparator, ATT-7, A'I'T-9, ATT-10,
ATT-11 are each attenuators. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (3)

[Claims] (1) An external microphone that converts audio into an electrical signal, a microphone amplifier that amplifies the signal, a receive signal amplifier that amplifies the demodulated receive signal from the receiver, and inputs the microphone amplifier output signal and the output of the receive signal amplifier, respectively. an analog switch that separates each input signal into two outputs according to a control input signal; a transmit signal amplifier that receives and amplifies the transmit signal and outputs it as a modulated signal to a transmitter; A power amplifier receives and amplifies the receiving system signal and drives the speaker, a speaker receives the output and receives an electrical signal and converts it into an audio signal, and a transmitting level amplifier receives and amplifies the transmitting system output of the analog switch. a rectifier for rectifying its output, a transmitting system smoothing circuit for smoothing its output, a receiving level amplifier for receiving and amplifying the receiving system signal of the analog switch, a rectifier for rectifying its output, and a transmitting system smoothing circuit for smoothing its output. Compare the output voltage of a receiving system smoothing circuit that smoothes the output voltage with the output voltage of the transmitting system smoothing circuit, and depending on which value is larger, the High or Low output changes, and the output becomes the control input of the analog switch. In a hands-free phone for a car phone equipped with a voltage comparator, each of the transmitting signal amplifier, transmitting level amplifier, power amplifier, and receiving level amplifier has two input terminals, and one input terminal is connected through an attenuator to the search signal amplifier. The one is an input terminal without an attenuator, and the gain can be changed by selecting either terminal, and when the output voltage of the smoothing circuit of the transmitting system is higher than the smoothing output voltage of the receiving system, the analog switch is activated by the output of the voltage comparator. is controlled to select the higher gain of the transmitting signal amplifier and the transmitting level amplifier, and the lower gain of the power amplifier and the receiving level amplifier, respectively, so that the smoothed output voltage of the receiving system is selected as the transmitting signal amplifier and the transmitting level amplifier, respectively. A hands-free telephone characterized in that when the system smoothed output voltage is larger than the system smoothed output voltage, the opposite gain is selected. (2) The transmitting signal amplifier and the power amplifier each have a gain change range of 10 to 20 dB, and the transmitting level amplifier and the receiving level amplifier each have a gain change range of 15 to 20 dB, according to claim 1. hands-free phone. (3) The number of input terminals between the transmitting level amplifier and the receiving level amplifier is 1 each for a fixed gain, the input terminal of the transmitting level amplifier is connected to the output of the transmitting signal amplifier, and the input terminal of the receiving level amplifier is connected to the power A hands-free telephone as claimed in claim 1 connected to the output of an amplifier.