JPH056927B2 - - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field The present invention transmits a signal obtained from a tape recorder or the like on a radio wave signal, receives the transmitted radio wave signal, and listens to the reproduced signal. The present invention relates to an audio device having such a structure. (b) Prior Art A device called a wireless headphone has been commercialized, which transmits signals reproduced by a stereo device, such as a tape recorder, on radio waves, and receives and listens to the transmitted signals. , As for the technology related to such a wireless receiving device,
For example, it is disclosed in Japanese Patent Publication No. 59-28300. (c) Problems to be Solved by the Invention An audio device using a conventional wireless headphone is configured to perform transmission and reception operations using radio waves of one frequency. When such equipment is used indoors, it will not interfere with radio waves transmitted by other people's audio equipment;
When used outdoors, a problem of interference occurs. The present invention aims to provide an audio device that is improved in this respect. (d) Means for Solving the Problems The present invention provides a method for transmitting signals obtained from a tape recorder or the like by a transmitting device configured to transmit signals at two different frequencies (F ₁ and F ₂ ). When an AFC circuit is built into a receiving device that receives a radio wave signal, and the pull-in frequency of the AFC circuit is f _c and the receiving frequency when there is no signal is F ₀ , F ₁ ≧ F ₀ − f _c ,
The relationship is such that F ₂ ≦F ₀ +f _c and F ₂ −F ₁ >f _c . (e) Effect The present invention makes it possible to switch the frequency of a radio wave signal transmitted from a transmitting device to two different frequencies, and to set the two frequencies within the range of the pull-in frequency of an AFC circuit incorporated in a receiving device. This setting eliminates the need for tuning operations in the receiving device. (F) Embodiment FIG. 1 shows an embodiment of the acoustic device of the present invention, and FIG.
The figure is a frequency relationship diagram for explaining the operation of the present invention. In FIG. 1, numeral 1 is a transmitting device incorporating a tape recorder, etc., and a magnetic head 2 for reproducing signals recorded on the magnetic tape;
A tape recorder circuit 3 has a built-in amplifying circuit for amplifying the signal reproduced by the magnetic head 2, and a transmission device that modulates the reproduced signal outputted from the tape recorder circuit 3 with FM modulation and transmits it from the transmitting antenna 4. It consists of a circuit 5 and a frequency switching switch 6 for switching the modulation frequency of the transmitting circuit 5. In such a configuration, the modulation frequency when the frequency selector switch 6 is in the position shown is
F ₁ , the modulation frequency is set to switch to F ₂ when switched to the opposite side of the illustrated position. 7 is a receiving device that receives the radio signal transmitted from the transmitting device 1 , and includes a radio antenna 8 that receives radio waves, a high frequency amplification circuit 9 that amplifies the high frequency signal obtained from the receiving antenna 8, and the high frequency amplification circuit. Signals obtained from 9 and oscillation circuit 1
a mixing circuit 11 that mixes the signal obtained from 0;
An intermediate frequency amplification circuit 12 which receives the intermediate frequency output from the mixing circuit 11 and amplifies the signal, a detection circuit 13 which receives the signal output from the intermediate frequency amplification circuit 12, and from the detection circuit 13. An AFC control circuit 14 that controls the oscillation frequency of the oscillation circuit 10 based on the obtained signal, an amplification circuit 15 that receives an audible signal output from the detection circuit 13 and amplifies the signal, and an amplification circuit 15 that amplifies the signal. The device comprises a headphone jack 16 to which the amplified signal is applied and into which a headphone plug is inserted. In such a configuration, the receiving frequency of the receiving device 7 when there is no signal is _F0 , and the AFC control circuit 14 operates to control the AFC.
If the range of the pull-in frequency of operation is f _c , the frequencies of the radio signal transmitted from the transmitting device 1 are F ₁ and F ₂
are set to satisfy the relationships F ₁ ≧F ₀ −f _c , F ₂ ≦F ₀ +f _c , and F ₂ −F ₁ >f _c . The present invention is constructed as described above, and its operation will be explained next. When the transmitting device 1 is in an inactive state, the receiving device 7
When a power switch (not shown) provided in the receiver is turned on, power is supplied to each circuit, and the receiver 7 enters a receiving operation state. In this state, since there is no radio wave signal transmitted from the transmitting device 1 , the receiving device 7 is in a state of receiving the signal of frequency _F0 . When the tape recorder incorporated in the transmitting device 1 is operated to reproduce in such a state, the tape recorder enters the reproducing operation state, and power is supplied to the transmitting circuit 5 to transmit radio waves. The signal reproduced by the magnetic head 2 is amplified by the tape recorder circuit 3 and then input to the transmitting circuit 5. The playback signal from the tape recorder circuit 3 inputted to the transmitting circuit 5 is FM modulated and transmitted from the transmitting antenna 4 at a frequency.
Sent in _F1 . The signal of frequency F ₁ sent out from the transmitting device 1 passes through a receiving antenna 8 provided in a receiving device 7 to a high frequency amplification circuit 9.
is input. In this state, the frequency of the oscillation circuit 10 is in a state in which it receives a signal of frequency _F0 , but since the frequency _F1 is within the pull-in frequency of the AFC circuit, the oscillation circuit 10 is oscillated by the action of the AFC control circuit 14. The oscillation frequency of the circuit 10 is changed, and the receiving device 7 enters a state in which it receives the signal of frequency F ₁ sent from the transmitting device 1 . The signal thus received is detected by the detection circuit 13, so that the reproduced signal from the tape recorder is input to the amplifier circuit 15. The reproduced signal inputted to the amplifier circuit 15 is amplified and then applied to the headphone jack 16, so that if a headphone plug is inserted into the headphone jack 16, the reproduced signal can be heard by the headphone. I can do it. Therefore, the user can listen to signals such as music played by the tape recorder built into the transmitting device 1 from a remote location. As described above, the playback and listening operation is carried out when the frequency selector switch 6 is in the state shown in the figure.Next, when the frequency selector switch 6 is in the playback and listening state, what happens when the frequency selector switch 6 is switched to the opposite side from the state shown in the figure. The operation will be explained. When the frequency selector switch 6 is switched to the opposite side from the state shown in the figure, the modulation frequency of the transmitter circuit 5 changes from _F1 to _F2 .
The receiving device 7 , which was in the state of receiving a signal with frequency F ₁ , becomes out of tune, and the reception frequency of the receiving device 7 becomes F ₀ , which is the frequency when there is no signal.
It is ready to receive the signal. When the receiving frequency by the receiving device 7 becomes F ₀ , the frequency F ₂ transmitted from the transmitting device 1 falls within the pull-in frequency of the AFC circuit. As a result, the oscillation frequency of the oscillation circuit 10 is changed by the action of the AFC control circuit 14, and the receiving device 7 enters a state in which it receives the signal of frequency F ₂ sent from the transmitting device 1 . Therefore, signals such as music reproduced by the tape recorder incorporated in the transmitting device 1 can be listened to on a headphone at a remote location. As explained above, when the transmitting frequency of the transmitting device 1 is switched, the receiving frequency of the receiving device 7 is automatically switched. Furthermore, even if a signal of frequency F ₂ sent from another transmitting device is input to the high frequency amplifier circuit 9 through the receiving antenna 8 forming _the receiving device 7 while receiving a signal of frequency F 1 , this frequency F ₂ is outside the pull-in frequency of the AFC circuit when it is in the state of receiving frequency _F1 , so it has no effect on the receiving operation of the receiving device 7 , and the receiving operation of frequency _F1 can be performed without any trouble. In this embodiment, a monaural transmitting/receiving device has been described, but it is of course possible to implement the present invention in a stereo transmitting/receiving device. Furthermore, although the case where the receiving antenna 8 is provided in the receiving device 7 has been described, the present invention can also be implemented in a device in which a cord connecting a plug inserted into the headphone jack 16 and the headphone is used as an antenna. (G) Effects of the Invention The present invention makes it possible to switch the frequency of a radio wave signal transmitted from a transmitting device to two different frequencies, and to switch the two frequencies into the range of the pull-in frequency of an AFC circuit incorporated in a receiving device. Since the transmitting frequency is set within the range, even if the transmitting frequency is changed, there is no need to perform a tuning operation on the receiving device side, resulting in excellent operability. In addition, since there is no need to provide an operation knob or a channel selection circuit on the receiving device side, the circuit configuration is simplified, and the present invention has a very large size when implemented in an audio device such as a wireless headphone. It is effective.

[Brief explanation of the drawing]

The circuit shown in FIG. 1 is an embodiment of the audio device of the present invention, and FIG. 2 is a frequency relationship diagram for explaining the operation of the present invention. Explanation of the main drawing numbers: 1 ... Transmitting device, 3... Tape recorder circuit, 5... Transmitting circuit, 6... Frequency selection switch, 7 ... Receiving device, 9... High frequency amplifier circuit, 10... Oscillation circuit, 11...mixing circuit, 12...intermediate frequency amplification circuit, 13...detection circuit, 14...AFC control circuit, 16...headphone jack.

Claims (1)

[Claims] 1. A transmitting device configured to transmit signals obtained from a tape recorder or the like using radio waves of two different frequencies, and a transmitting device configured to receive radio wave signals transmitted from the transmitting device and incorporating an AFC circuit. In an acoustic device consisting of a receiving device, the two frequencies transmitted from the transmitting device are F ₁ and F ₂ , the receiving frequency of the receiving device when there is no signal is F ₀ , and the pull-in frequency of the AFC circuit is f _c An acoustic device characterized in that the following relationship is established: F ₁ ≧F ₀ −f _c F ₂ ≦F ₀ +f _c F ₂ −F ₁ >f _c .