KR880001016B1 - Radiotelephone with hand-free operation - Google Patents

Abstract

The appts. includes a microphone, a speaker, and a control circuitry. The control circuitry of speakerphone interfaces a microphone to a transmit signal and speaker to a receive signal of a duplex communication path, such as a radio channel or telephone line. An audio switch opens or closes the microphone audio path in response to the binary complement of the control signal. Transmit and receive signal detectors each includes a logarithmic amplifier, an envelope detector, a smoothing filter, a valley detector, a summer and a comparator for detecting the presence of audio signals in environments that may be subject to high background noise.

Description

Hand free cordless telephone

1 is a schematic configuration diagram of a vehicle wireless system using the hand-free control circuit according to the present invention usefully.

2 is a detailed block diagram of a hand-free control circuit according to the present invention.

3 is a detailed circuit diagram of the control logic portion of the hand-free control circuit in FIG.

* Explanation of symbols for main parts of the drawings

100: car wireless telephone system 110: car wireless

111: microphone 112: speaker

113: control and dialing unit 101: car

103: satellite receiver 102: base station

104: control terminal 105: telephone central station

201: gain stage 202: sound switch

205: high pass filter 200: control circuit

213: gain stage 214: scanner

220: car wireless receiver 221: duplex

222: wireless transmitter 230: control circuit

The present invention relates generally to automotive and portable wireless systems, and more particularly to circuitry for providing hand free operation to automotive and portable wireless users in such wireless systems.

In wireless and wireline telephone systems, a user has talked on a handset that includes a speaker at one end positioned proximate the user's ear and a microphone at the other end proximate the mouth. Therefore, one hand is holding the telephone handset so that the user is free only one hand. In order to provide users with a higher degree of convenience, speakerphones have been developed in wireline telephone systems. Usually, these speakerphones choose a width that is louder by comparing the volumes on both sides. These conventional speakerphones are well suited for use in landline telephones, but cannot operate correctly due to the high ambient noise generated in automobiles when used wirelessly. For example, high levels of ambient noise cause these speakerphones to always select only the hands-free side, thus blocking all calls from the other side.

One form of hand-free operation is in a wireless system by utilizing a switch that operates the wireless transmitter and applies a voice signal from the speaker. However, whenever you want to talk on the hand-free side, you must activate the footswitch. Therefore, the handfree side does not have complete freedom of operation as in the case of the speakerphone. Full freedom of movement is extremely important when driving a car on a handprint. Restrictions on the operation of actuating the footswitch may cause an accident or damage to life. Therefore, conventional speakerphones or foot switch operated transmitters do not provide the form of hand free operation required in automobiles.

It is therefore an object of the present invention to provide an improved circuit which enables the handsfree side to make a handsfree voice call with complete freedom of operation.

It is yet another object of the present invention to provide an improved circuit that allows for hand-free voice calls in an atmosphere of high levels of ambient noise.

It is a further object of the present invention to provide an improved circuit which allows switching between two parties to be carried out automatically and evenly so that the two parties are in good condition with each other and to allow a hands-free voice call between the two parties.

Briefly, the improved control circuit of the present invention controls the application of voice signals from a call path, such as a wireless channel, to a utilization circuit, such as a speaker, and the application of sound signals from a sound signal source, such as a microphone, to a call path. . The control circuit includes first and second delay circuits to which sound signals from the communication path and the microphone are supplied, respectively, to generate an output signal indicative of the presence of sound signals. Here, each output signal indicates that it exists for a predetermined time interval after an interval where no audible signals are present. The output signals from the first and second delay circuits are connected to control circuits in which the first and second switching circuits generate control signals such that the acoustic signals are applied to the speaker in the call passage and the acoustic signals are respectively applied to the call passage in the microphone. do. When the output signal of the first delay circuit is absent for a predetermined time interval and when there is an acoustic signal at the microphone, the control signal is in a first state for applying the acoustic signal to the communication passage at the microphone. Becomes The second state of the control signal applies an acoustic signal to the speaker in the call passage when the second delay circuit output signal indicates when the output signal from the microphone has been absent for a predetermined period and there is an acoustic signal present in the call passage. . Therefore, when one acoustic signal is selected and the other acoustic signal is absent for a predetermined time interval, automatic switching is provided between the acoustic signal in the call path and the acoustic signal in the microphone.

In FIG. 1, there is shown an automobile radiotelephone system 100 that utilizes a handfree control circuit embodying the present invention. In a conventional cordless telephone system, i.e., a system such as the IMTS (Improved Mobile Telephone Service), the user in the vehicle 101 is connected to the base station 102 interconnected by the control terminal 104 to the landline central station 105. Talk as the car radio 110. This control terminal 104 includes a control circuit 131 and a hybrid 132, the control circuit 131 and the hybrid 132 is a subscriber line interconnected to the base station 102 and the telephone central station 105 Or it provides a communication path between the relay lines. The number dialed on the vehicle side by means of the control and dial unit 113 is received at the control terminal 104 and transmitted to the subscriber line or relay line of the telephone central station 105. The central office 105 receives the dialed telephone number and connects the automobile side to the required wired side. Similar processing is utilized when the wireless user dials the number on the car side. Such cordless telephone systems also include portable (portable) wireless devices of the type described in US Pat. Nos. 3,906,166 and 3,962,553. Such portable radios can be tied by a user and can be operated, for example, at his workplace or in a car. For details of the circuit characteristics and signal processing for the control terminal 104, see the Motorola Service Manual 68 _p 81028 _E 65, for the base station 102 the Motorola Service Manual 68 _p 81033 _E 10, and the automotive radio ( 110) and the control dialing unit 113, see the Motorola Service Manuals 68 _p 81039 _E 25, 68 _p 81029 _E 65 and 68 _p 81037 _E 85, all of which are known by the Motorola Service Bulletin.

This conventional radiotelephone system may include a satellite receiver 103 that can cover a large area so that transmissions in the car radio 110 are well received. The base station 102 includes a high power transmitter 120 located centrally in the earth's area so that the transmission here can reach all of the vehicle radios 110 in the earth's area. However, transmissions in the automotive radio 110 with very low power transmitters may not always reach the base station receiver 121 but may continue to be received by one of the satellite receivers 103.

In order for the automobile side to receive the same form as the telephone service received by the landline, each radio channel of the radiotelephone system needs to be a dual radio channel with separate transmission and reception frequencies. Therefore, the vehicle radio 110 transmits at one frequency and receives at the other frequency simultaneously, so that the vehicle and the wireline can speak and listen at the same time. Control and dialing unit 113 typically includes a handset similar to a handset commonly found in landline telephony equipment. It is necessary to lift the handset to the ear, just as the car does on the wired side. However, if the conversation during the telephone call can be achieved without the need for any physical action, it provides the vehicle side with great convenience and safety. By utilizing the hand-free control circuit of the present invention, the vehicle side can communicate with the wired shaft during the call period without the need for physical movement, thereby preventing the vehicle side from interfering with safe driving of the vehicle. In addition, some vehicle regulations require that the vehicle be stopped when the vehicle dials the other party's number. This need is regulated to ensure the safety of the automobile and the public. Because the distraction of the car side during the dialing process can cause a car accident. As a result, many new wireless telephone control and dialing units 113, which are as described in US Pat. Nos. 4,122,203 and 4,220,820, provide for automatic dialing of telephone numbers stored in memory. However, the handcept had to be removed from this unit for the conversation. By utilizing the present invention, the new hand-free control circuit further enhances vehicle safety by allowing the vehicle side to communicate without having to move one hand at the steering wheel.

A separate microphone 111 and a separate speaker 112 are provided for voice calling to provide hand-free operation for automotive applications. In addition, in a wired application, the microphone and speaker in the handset of the control and dialing unit 113 may be applied to the hand-free side. It is an advantage to utilize the separate microphone 111 in the vehicle to receive the hand free voice. As a result, it was found that the optimum mounting position for the microphone 111 in the vehicle is on the inner line of the roof of the vehicle or the front of the awning plate or the awning plate. These locations indicate that ambient noise pickup is minimal and voice pickup is best. This mounting position also provides some cushioning of interference vibrations. The omnidirectional electrode microphone cartridge was found to be very good and efficient.

Referring to FIG. 2, a detailed block diagram of a hand free control circuit 200 embodying the present invention is shown. The hand-free control circuit 200 may be located in the car radio 110 of FIG. 1 or in a separate equipment box utilized in a conventional cordless phone to interface the car radio 110 with the control and dialing unit 113. .

In FIG. 2, the hand-free control circuit 200 shares and connects the microphone 111 and the speaker 112 to the wireless transmitter 222 and the receiver 220, respectively. The two voice switches 202 and 212 are closed or blocked to pass the acoustic signal at the microphone 111 or the acoustic signal to the speaker 112 in response to the control signal at the control logic 230. To open. Therefore only one passage is closed by the acoustic switches 202 and 212 at any given time. In an embodiment, the acoustic switches 202 and 212 are junction FET transistor switches without a transition state. Each of the acoustic passages also includes gain stages 201 and 203 in the microphone acoustic passage and gain stages 211 and 213 in the speaker acoustic passage. The amplifier 213 in the speaker sound path has a variable gain adjusted by the vehicle side to control the volume of the speaker 112.

The acoustic signals in the microphone sound path are applied from the amplifier 203 to the radio transmitter 222, which supplies radio signals to the duplexer 221 for transmission through the antenna 23. The radio signals received by the antenna 223 are selectively applied to the radio receiver 220 by the duplexer 221, which is acoustic in radio signals for application to the amplifier 213 and the syringe 214 in the speaker acoustic path. Demodulate the signal. In a cordless telephone system, the wireless transmitter 222 typically runs for the entire duration of the call. However, in order to save power in battery operated transmitters (ie as used in portable radios described in US Pat. Nos. 3,906,116 and 3,962,553), the radio transmitter 222 is communicated by an automobile or portable side. It can only be driven by the transmission key signal during the time required. Therefore, since the radio transmitter 222 does not operate during the duration of the call, the base station receivers 103 and 121 are squelch based on the detection of, for example, the presence or absence of a supervisory sound tone in the radio transmitter 222. A squelch circuit like the circuit is needed. The car cordless telephone is described in the above Motorola instruction manual 68 _p 81039 _E 25 and by Albert J. The title "Portable Cordless Phone for Organizational Systems," by Leach and Donald L. Linder, and Michigan Dearborn, described in a publicly known technique at the 30th Annual Meeting of the Automotive Technology Company, September 15-17, 1980. . Details of conventional circuits utilizing the transmitter 222, duplexer 221 and receiver 220 are described in the Motorola instruction manuals 68 _p 81039 _E 25, 68 _p 81029 _E 65 and 68 _p 81037 _E 85 described above.

In addition, the hand-free control circuit 200 in FIG. 2 includes auto-attached and wired-side signal detectors 206 and 207, respectively, for detecting the presence of the vehicle-side voice signal and the wired-side voice signal. If the microphone 111 does not provide a high pass response, the high pass filter 205 may be inserted between the microphone 111 and the automobile side signal detector 206. The microphone signal is first high pass filtered to remove ambient noise from the car, which is concentrated at low acoustic frequencies. A high pass filter with a cutoff frequency of approximately 300 Hz filters most of this low frequency ambient noise. Similar high pass filters are usually provided in the automotive wireless receiver 220. If the automotive radio receiver 220 does not include such a high pass filter, a high pass filter similar to block 205 is hidden to filter the receiver signal. In addition, in applications not characterized by such low frequency ambient noise, a highpass filter such as block 205 is eliminated in the acoustic path.

Automotive side and wire side signal detectors 206 and 207 include identical circuit blocks 240-244. Blocks 206 and 207 are logarithmic amplifiers 240 (commonly referred to as "soft" limiters). A conventional circuit including an envelope (envelope) detector 241, a valley detector 242, a summer 243, and a comparator 244. The logarithmic amplifier 240 extends the dynamic range of the detector 241 due to the amplification characteristic. Envelope detector 241 provides an output that conforms to the maximum and minimum of the acoustic signal. The belly detector 242 provides an output that tracks the minimum of the envelope detector output. Essentially the bell detector output corresponds to the steady state ambient noise present at the microphone 111 in the case of detector 206 or at the receiver 220 in the case of detector 207. Summer 243 adds the reference voltage V _R to the belly detector output. By adding the off-cell voltage V _R to the belly detector output, the comparator 244 will not generate a spurious output signal due to the presence of ambient noise. Therefore, comparator 244 will provide an output signal if the envelope detector output does not exceed steady state ambient noise by the amplitude of the reference voltage V _R. The offset voltage V _R is selected simultaneously with the response characteristic of the envelope detector 241 to avoid the generation of the spurious comparator output signal due to the ambient noise present in the vehicle. The output signal from the comparator 244 has a high voltage level when the envelope detector output exceeds the belly detector output by the offset voltage V _R and provides a low voltage level to the control circuit 230. The high voltage level at the comparator 244 indicates that an acoustic signal at the microphone 111 was detected in the case of the detector 206 and an acoustic signal at the receiver 220 was detected in the case of the detector 207.

The adder 214 applies the summation signal of the sound signal from the FM receiver 220 and the sound signal from the sound switch 212 to the detector 207. The amplifier 213 is variable gain controlled so that the vehicle side adjusts the volume of the speaker 112. Therefore, the signal applied to the detector 207 by the summer 214 changes as the volume of the speaker 112 changes. The balance between the signal levels applied to the wireline side signal detector 207 and the automobile side signal detector 206 is maintained by increasing the signal level applied to the detector 207 so that the volume of the speaker 112 is increased. As a result, the rise and fall times of detectors 206 and 207 are communicated over the volume area of speaker 112. This structure avoids unnecessary switching between the microphone sound path and the speaker sound path. In addition, in this structure, the volume increase of the speaker 112 allows the microphone sound path to remain closed once the speaker sound path is opened at the vehicle side.

The control logic 230 in FIG. 2 responds to the output signals from the automobile and wireline side signal detectors 206 and 207. The control circuit 230 provides a control signal for opening or closing the sound switch 212 and the sound switch 202 through the inversion gate 204. When the sound switch 212 is opened, the sound switch 202 is in the reverse order of closing. The control circuit 230 also responds to the squelch signal from the wireless receiver 220 to block the output signal from the wired side signal detector 207 when the wireless signal is not received by the receiver 220. When the vehicle side speaks, the control circuit 230 provides a transmission key signal for turning on the transmitter 222.

The control circuit 230 in FIG. 2 is shown in more detail in the circuit diagram of FIG. In FIG. 3, the control signals for the acoustic switches 202 and 212 are provided by latches comprised of the NOR gates 301 and 302. When the NOR gate 302 is in binary 1 state, the sound switch 212 is closed and the sound switch 202 is developed and when the NOR gate 202 is in binary state, the sound switch 202 is closed and the sound switch 212 is closed. ) Is opened. When the acoustic switches 202 and 212 are closed, the switches pass acoustic signals, and when the switches 202 and 212 are opened, they block the acoustic signals. The final speaker operation on the wired side is that the output signal from the wired side signal detector 207 is not present for the time interval selected by the delay circuits 321 to 327 and the output signal of the automobile side signal detector 206 is not on the automobile side. In the case of indicating that is speaking in, the sound switch 202 is closed in the microphone 111 so as to pass the sound signal to the transmitter 222. Similarly, the final speaker operation on the automobile side is that the output signal from the automobile side signal detector 206 is absent for the time defined by the delay circuits 310 to 312 and the output signal from the wireline side signal detector 207 is not on the wired side. When indicating that it is speaking, the receiver 220 is closed to pass an acoustic signal from the receiver 220 to the speaker 112.

Referring to FIG. 3, the NOR gate 302 will be set to the binary zero state (low voltage level) by the binary one state (high voltage level) at the NOR gate 304. The output signal from the detector 206 detects a horse on the automobile side, and the output signal from the wired side signal detector 207 has a binary zero state for a time interval selected by the delay circuits 321 to 327. NOR gate 304 provides a binary one state at the output when the binary one state is present. When the NOR gate 303 is in binary 1 state, the NOR gate 302 will be set to the binary 1 state that drives the acoustic switch 212. NOR gate 303 when the output signal from detector 207 is in binary one state and the output signal from detector 206 is in binary zero state for a time interval selected by delay circuits 310 to 312. ) Provides a binary zero state at the output. Delay circuits 310-312 and 321-327 have fast charge paths provided by diodes 310 and 325, respectively. Therefore, when the output signal from the detector 206 changes to the binary one state, the diode 310 bypasses the resistor 311 so that the capacitor 312 is quickly charged to a high voltage level. In addition, the diode 325 bypasses the resistors 322, 321, and 324 so that the capacitor 327 quickly charges to a high voltage level when the output signal from the detector 207 is charged in binary binary state. Pass. The delay circuits 310 to 312 and 321 to 327 respectively change the output signal from the detectors 206 and 207 from the binary 1 state to the binary 0 state and discharge from the high voltage level to the low voltage level. When the delay interval is provided. Therefore, according to the present invention, the acoustic path switching which is commonly applied to both as a break-in means that the other delay circuits 310 to 312 or 321 to 327 are discharged to the low voltage level. It is detected and activated immediately. However, if the side of the acoustic path currently closed continues to speak, then its delay circuits 310 to 312 or 321 to 327 will remain charged at a high voltage level to prevent operation of the other side. will be.

The time intervals of the delay circuits 310 to 312 and 321 to 327 are set in consideration of the minimization of the operating characteristics and the minimum spurious and the rapid brine-in at high ambient noise. It has been found that the time interval chosen to be approximately 250 ms (range of 200 to 300 ms) is suitable for delay circuits 310 to 312 for the west side brate-in. Therefore, in a preferred embodiment, capacitor 312 and resistor 311 have a time constant of approximately 250 ms. However, the time interval for the delay circuits 321 to 327 is related to the magnitude of the output signal interval at the detector 207. In an embodiment, the delay circuits 321-327 provide a short time interval of about 50 ms for the output signal from the wired side signal detector 207 with short intervals and of the wired side signal detector 207 with long intervals. The output signal provides a longer time interval in the range of approximately 160ms. Therefore, the time interval provided by the delay circuits 321 to 327 is between a minimum of 50 ms and a maximum of 160 ms. For example, the time interval provided by the delay circuits 321 to 327 may be proportional to the interval of the output signal at the wireline side signal detector 207 over a range of 50 ms to 160 ms. In general, the time interval of the delay circuit varies from 30 to 200 ms. When a minimum delay value is selected, such as 30 to 50 ms, a spurious signal is avoided when a call is interrupted due to a delay of a signal passing through the control terminal 104 and the telephone central station 105. It will always be necessary. In an embodiment, capacitor 327 and resistor 326 have a time constant of approximately 50 ms and capacitor 323 and resistor 322 have a time constant of approximately 160 ms.

The above-described feature of the present invention enables the microphone acoustic path at the vehicle side when the radio signal received by the radio receiver 220 of FIG. 2 exhibits multipath fading. During multipath fading, receiver 220 outputs a short burst of wired side conversation depending on the fading in or out of the radio signal. If these bursts are relatively short, when the vehicle side wants to speak, the vehicle side can continue to close the microphone sound path because the time interval of the delay circuits 221 to 227 is shorter than in this case.

According to another feature of the invention, the squelch signal in the wireless receiver 220 of FIG. 2 performs a film roll on the output signal of the detector 207 by the method of the inverting gate 331 and the AND gate 330 of FIG. It is utilized. When the radio signal is not received by the radio receiver 220, the squelch signal is in binary 1 state so that the AND gate 330 blocks the output signal from the detector 207, and the radio signal is in the radio receiver 220. The squelch signal is in binary zero state so that AND gate 330 passes the output signal at detector 207 when received by. If no squelch signal is provided at the receiver 220, the jumper 332 grounds the input to the inverting gate input 331 such that the AND gate 330 continuously passes the output signal at the detector 207. It is used to make In addition, such a squelch signal is detected by the wireline signal detector 207 in the same manner as the noise burst from the receiver 220, that is, the normal wired voice signal, which prevents the noise microphone sound path on the automobile side from being closed. Used to prevent noise bursts.

According to another feature of the invention, the control circuit 230 in FIG. 3 may provide a transmission key signal to the radio transmitter in FIG. 2 In FIG. 3, the transmission key signal provided by the NAND gate 305 Becomes the binary 0 state to drive the radio transmitter 222 when the NOR gate 301 becomes the binary 1 state and the Q output of the timer 340 becomes the binary 1 state. The NOR gate 301 is in binary 1 state when the microphone sound path is closed. The timer 340 may be a conventional monostable multivibrator triggered by a high propagation transition of the output signal at the detector 206 indicating that a car side conversation has been detected. The time interval of the timer 240 must be chosen as at least 500 ms to bridge the space between consecutive words.

In FIG. 3, logic circuits 301-307, 330, 331, and 340 are used in conventional integrated circuits, such as CMOS integrated circuits described in "CMOS Integrated Circuits" published by Texas, Austin, Motorola Semiconductor Corporation in 1978. It can be configured by utilizing a circuit element of.

The hand free control circuit of the present invention can be usefully utilized in a wide range of applications where one side needs to have full freedom of operation. Therefore, the hand-free control circuit of the present invention can be utilized to provide a hand-free call to the automobile side in the automobile radiotelephone system and also to the wired side in the landline system. The present invention provides a hand free call in the presence of a high level of ambient noise. In addition, the new hand-free control circuitry allows quick connection to both sides and minimizes spurious sound path switching.

Claims (10)

Detects an acoustic signal received in a radiotelephone larger than a threshold so as to control the application of the acoustic signal received by the radiotelephone to the speaker and the application of the acoustic signal from the microphone 111 to the radiotelephone. A first detection circuit 207 for generating a first output signal having a first predetermined state at a time and generating a second output state at the absence of an acoustic signal, and detecting the presence of an acoustic signal from a microphone larger than a threshold; A second detection circuit 206 for generating a second output signal having a first expected state in the presence of an acoustic signal and having a second expected state in the absence of an acoustic signal, and each time the first circuit has a first expected state A first delay in response to the first output signal to generate an output signal having a first predetermined state and having a second predetermined state at a predetermined time interval after the first circuit output signal has the second predetermined state; Furnaces 321 to 327, each time the second circuit output signal has a first predetermined state, and having a first predetermined state, and having a second predetermined state at a predetermined time interval after the second circuit output signal has a second predetermined state. Second delay circuits 310 to 312 responding to the second output signal to generate an output signal, and when the acoustic signal from the microphone is present, has a first predetermined state and when there is an acoustic signal received by the wireless telephone A control circuit 230 that responds to the first and second delay circuit output signals and the first and second detection circuit output signals to generate a control signal having a second predetermined state; And a first acoustic switch 202 responsive to the first predetermined state of the control signal, and a second acoustic switch 212 responsive to the second predetermined state of the control signal to apply the acoustic signal to the speaker in the wireless telephone. Wireless i The control circuit may be configured to control the application of the acoustic signal received from the wireless receiver 220 to the speaker in the wireless channel and the application of the acoustic signal from the microphone to the wireless transmitter 222 in transmission on the wireless channel. And wherein the wireless receiver has a predetermined sound band and the control circuit comprises an acoustic signal filter circuit operating in the presence of varying background noise, the first detection circuit 207 and the second detection circuit 206 Means for dynamically varying the threshold with background noise, and a high pass filter 205 for high-passing the acoustic signal from the microphone, the control circuit comprising a first predetermined state and a second delay circuit of the first detection circuit; Generates a second predetermined state of the control signal in response to the second predetermined state of the output signal of the first signal, and outputs the first predetermined state of the second detection circuit output signal and the output signal of the first delay circuit. It is applied to generate a first predetermined state of the control signal in response to the second predetermined state, and the control circuit is applied to maintain the state of the control signal when no acoustic signal is detected by the first and second detection circuits. The first sound switch 202 responds to a second predetermined state of the control signal to block the sound signal from the microphone, and the second sound switch 212 controls the sound signal to block the sound signal from the wireless telephone. And to respond to a first scheduled state of the wireless telephone. The radiotelephone according to claim 1, wherein said first delay circuit comprises means for varying a time interval provided in proportion to the duration of an acoustic signal from the radio receiver. 3. A radiotelephone according to claim 2, wherein said time interval varying means varies the time interval of said first delay means between 30 and 200 ms. 4. A radiotelephone according to claim 1 or 3, wherein the time delay of the second delay means is at least 200 ms. The control circuit according to claim 1, wherein the wireless telephone is activated by a transmission key signal in a first scheduled state and stopped by a transmission key signal in a second scheduled state, and the control circuit is controlled by a control circuit in a second scheduled state and a first scheduled state. And a gate (305) for generating a transmission key signal having a first predetermined state or having a second predetermined state in response to the second output signal of the state. 6. The wireless communication system of claim 5, further comprising: a wireless receiver (220) for generating a squelch signal having a first expected state when a wireless signal is present and having a second expected state when no radio signal is present; Providing a first output signal of the same state as generated by the first detection means when having a first predetermined state; providing a first output signal of a second expected state when the squelch signal has a second predetermined state; And a gate (330, 331) disposed between the first detection means and the control circuit to couple the first output signal. The control circuit according to claim 5, wherein the control circuit generates an output signal in response to the first scheduled state of the second output signal having the first predetermined state or the second predetermined state for a predetermined time interval, A timer 340 disposed between the detection means, and the gate 305 generates a transmission key signal having the first scheduled state in response to the control signal of the second scheduled state and the output signal of the timer of the first scheduled state. Cordless telephone specializing in doing. 2. The radio signal receiver of claim 1, wherein the amplifier 213 amplifies the audio signal by a second switching means applied to the first detection means, an adder 214 that sums the audio signals from the radio receiver, and a predetermined amplification factor. And the second switching means. The radiotelephone according to claim 8, wherein said amplifier (213) has a variable amplification factor. 2. The apparatus of claim 1, wherein the first and second detector circuits include an algebraic amplifier 240 for algebraically amplifying an audio signal, an envelope detector 241 for filtering signals that deviate from a maximum or minimum value of a signal of an algebraic amplifier, A belly detector circuit 242 for dynamically detecting the minimum value of the signal from the envelope detector; a summer 243 for summing the minimum value and the reference voltage detected by the belly detector circuit; and a signal and envelope detector circuit of the summer detector. When the signal of the envelope detection circuit generates the output signal of each detection circuit in the first scheduled state when the signal of the envelope detection circuit is larger than the adder signal by comparing A wireless telephone, characterized in that configured to generate an output signal of

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