JPH0239907B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a wireless telephone that wirelessly transmits and receives signals between a base unit connected to a telephone line and a plurality of slave units.

(B) Background technology Recently, in wireless telephones that are connected to a telephone line and have been made possible to make wireless calls even when the base unit is connected to a slave unit that is located at a distance, it is now possible to connect a base unit to a single base unit in order to increase usage efficiency. For this purpose, a plurality of slave units are provided. By the way, the base unit and the slave unit are each provided with a transmitting circuit and a receiving circuit, and the transmitting circuit modulates a carrier wave with a calling signal, dial signal, or transmitting/receiving signal and transmits radio waves, and the receiving circuit receives and demodulates the radio waves. The radio waves transmitted from the base unit and the radio waves transmitted from the slave units have different frequencies, but each slave unit communicates by converting them to the original signals. The radio waves transmitted to the machine may use the same frequency. In such devices, when one handset uses another handset to transmit radio waves during communication, co-channel interference occurs, which interferes with normal telephone communications.

(C) Means for Solving Problems The present invention provides that if a handset is in use, even if another handset tries to make a call and turns the manual hook switch of the handset to on/off, the handset is automatically turned off. To provide a wireless telephone that prevents interference by stopping the radio waves transmitted by the telephone.

(d) Embodiment The present invention will be described below with reference to the drawings. In FIG. 1, 1 is a base unit connected to telephone lines L ₁ and L ₂ , and is used to connect to telephone lines L ₁ and L ₂ . interface section 2, a transmission circuit 3 that modulates carrier waves with the calling signal and reception signal from the telephone lines _L1 , _L2 , demodulates the radio waves transmitted from the slave units 5a, 5b, etc., and generates a dial signal and reception signal. a receiving circuit 4 that extracts the radio waves, and antennas 6 and 7 that transmit and receive the radio waves.
and has. The slave units 5a, 5b..., like the base unit 1, have a transmitting circuit 8 , a receiving circuit 9 , an antenna 10,
It has 11. From the base unit 1 to the slave units 5a, 5b...
The frequency of the carrier wave transmitted to is _f1 , and each slave unit 5
The frequencies f ₂ of the carrier waves transmitted from a, 5b, . . . to the base unit 1 are all the same frequency.

FIG. 2 shows a block diagram of the slave units 5a, 5b, etc., in which the transmitting circuit 8 includes the microphone 12,
A low frequency amplification circuit 13 that amplifies the audio signal from the microphone 12, an FM modulation circuit 15 that modulates the carrier wave generated by the carrier wave oscillation circuit 14 with the audio signal, and a multiplier circuit 16 connected to the FM modulation circuit 15. , and a high frequency output circuit 17,
Furthermore, the FM modulation circuit 15 includes a dial oscillation section 18.
A dial signal from is added. Also, the receiving circuit 9
is a high frequency amplification circuit 19, a mixing circuit 21 that mixes the high frequency signal from the high frequency amplification circuit 19 and a local oscillation signal from the local oscillation circuit 20 to generate an intermediate frequency signal, and an intermediate frequency amplification circuit that amplifies the intermediate frequency signal. 22, a detection circuit 23 that detects a voice signal and a calling signal from the amplified intermediate frequency signal;
a low frequency amplifier circuit 2 connected to the detection circuit 23;
4. A selective amplifier circuit 25 that amplifies the calling signal in the low frequency amplifier circuit 24, an audio output circuit 26 whose amplification degree is controlled by the calling signal, a speaker 27, and an audio output control circuit 28 that detects the calling signal. It becomes more. Furthermore, slave units 5a and 5b
. . is a line monitoring circuit 3 controlled by a signal from the intermediate frequency signal detection circuit 29 of the receiving circuit 9 and a calling signal from the audio output control circuit 28.
0 and transistors 31, 32, 33, and 34, and includes a switch circuit 35 controlled by the output signal from the line monitoring circuit 30. The line monitoring circuit 30 includes a NOR circuit 36 and an inverter 37.

Next, the operation of the wireless telephone according to the present invention will be explained. In the standby state, the switch switches 38 and 39 are in the state shown, and only the receiving circuit 9 is in the operating state. In such a state, when a calling signal from the other party is supplied to the base unit 1 via the telephone lines L ₁ and L ₂ , the calling signal modulates a carrier wave in the transmitting circuit 3 of the base unit 1 and transmits it together with the carrier wave f _{1 .} Sent. Said carrier f ₁
is applied to the slave units 5a, 5b, . . . receiving circuit 9, and is amplified by the high frequency amplification circuit 19. Then mixing circuit 2
1, it is mixed with a local oscillation signal and converted into an intermediate frequency signal, which is amplified by an intermediate frequency amplification circuit 22, and further converted into an audio signal by a detection circuit 23. The audio signal is amplified by a low frequency amplifier circuit 24, and then converted into an audio signal. The signal is supplied to the speaker 27 via the output circuit 26 and drives the speaker 27. As a result, handsets 5a, 5b...
The holder of the phone learns that the call has come. After that, the contact pieces 38a, 39 of the hook switches 38, 39
When a is switched to contacts 38c and 39c, the transmitting circuit 8 is also put into operation. Therefore, the microphone 12
When someone speaks, the speaking voice is converted into an electrical signal and amplified by a low frequency amplification circuit 13, a carrier wave _f2 oscillated by a carrier wave oscillation circuit 14 is FM modulated by an FM modulation circuit 15, and a multiplier circuit 16 modulates the carrier wave f2. The signal is multiplied and transmitted from the antenna 10 through the high frequency output circuit 17. The transmitted carrier wave f ₂ is received by the base unit 1, converted into the original audio signal by frequency conversion, detection, etc. in the receiving circuit 4, and after amplification is transmitted to the other party via the telephone lines L ₁ and L ₂ . Ru. In this way, it is possible to make a wireless call from a remote location to a base unit connected to a telephone line.

Although the case where a calling signal is transmitted from the other party has been described above, it is also possible to call the other party from the handset. In that case, first switch 3
The contact pieces 38a, 39a of 8, 39 are connected to the contacts 38b, 3
From 9b, the contacts 38c and 39c are switched to put the transmitter circuit 8 into operation. And dial oscillation section 1
When a dial signal is sent from 8, the carrier wave is FM modulated by the FM modulation circuit 15, and after being amplified as described above, it is transmitted from the antenna 10. The carrier wave is reproduced into an audio signal by base unit 1, and the dial signal is extracted.
It is transmitted to the other party via telephone lines L ₁ and L ₂ .

By the way, when communicating using one handset, if the transmitting circuit 8 of another handset is activated, the carrier wave f ₂ will be oscillated, which will interfere with the handsets that are already communicating. Therefore, when one slave unit is used, the transmitting circuit 8 is not activated even if the contacts 38a, 39a of the switch 38, 39 of another slave unit are switched to the contacts 38c, 39c. That is, the output of the intermediate frequency signal detection circuit 25 of the receiving circuit 9 of the handset 5a becomes low level only when the calling signal and the receiving signal are being received.
Further, the output of the audio output control circuit 28 is set to a low level only when there is a calling signal. When neither a calling signal nor an answering signal is currently being received by the receiving circuit 9 , the intermediate frequency signal detecting circuit 29
Since the outputs of the and audio output control circuits 28 are both high level, the output of the line monitoring circuit 30 is low level, and the transistor 31 of the switch circuit 35 is turned off and has no effect.
When a calling signal from the other party is received, the outputs of the intermediate frequency signal detection circuit 29 and the audio output control circuit 28 become low level, but the output of the line monitoring circuit 30 is still low level, so the switch circuit 35 remains unchanged. is in a state of Next, when the first slave unit is operated and communication begins, the carrier wave _f1 transmitted from the base unit is modulated by the reception signal, so the output of the intermediate frequency signal detection circuit 29 is held at a low level, but the audio The output of the output control circuit 28 is at a high level since there is no calling signal. Therefore, the output of the line monitoring circuit 30 is switched to high level. Then, transistor 31 is turned on, thereby turning on transistors 32 and 33 and turning transistor 34 off. Therefore, the holder may accidentally touch the contacts 38a and 38 of the hook switches 38 and 39.
Even if 39a is switched to contacts 38c and 39c, the transistor 34 is not turned on and the voltage of the battery 40 is cut off, and no power is supplied to the transmitting circuit 8. Therefore, the transmitting circuit 8 operates and does not transmit unnecessary carrier waves. . At this time, even if the switch 38, 39 is switched as described above by turning on the transistor 32, the voltage is applied from the battery 40 to the line monitoring circuit 30 through the transistor 32, so that the above state is maintained.

In addition, in order to put the child unit into operation, connect the contact pieces 38a and 39a of the switch switches 38 and 39 to the contact point 38.
When switching to 39c and 39c, the voltage supply to the line monitoring unit 30 is blocked, so the carrier wave transmitted from the base unit contains a conversation signal, and the output of the intermediate frequency signal detection circuit 29 becomes low level. Therefore, even if the output of the audio output control circuit 28 becomes high level, the output of the line monitoring section 30 will not become high level, so the transmitting circuit 8 will not be forcibly disabled.

(E) Effect As described above, the wireless telephone of the present invention uses a line monitoring circuit to monitor the output signals from the intermediate frequency signal detection circuit and the audio output control circuit for selectively amplifying the calling signal, so that the switch circuit is When the switch is in the standby state, the switch circuit is not activated even if a call signal is received, and the switch is switched to the communication state. However, when another handset is communicating, an intermediate frequency signal is detected and the switch circuit is activated. Therefore, even if the switch is switched to the communication state, the slave unit cannot be switched to the communication state.

In addition, after the switch circuit is activated, the line monitoring circuit is supplied with power supply voltage through the second transistor instead of the switch, so once the switch circuit is activated, the power supply voltage is supplied to the line monitoring circuit until the communication with other handsets is completed. After deactivating the transmission circuit of the slave unit and switching the slave unit to a communication state without communication with other slave units,
Since no power supply voltage is supplied to the line monitoring circuit through the switch, even if an intermediate frequency signal occurs, the switch circuit will not be activated and the transmitting circuit will not be inoperable.

[Brief explanation of drawings]

FIG. 1 is an overall block diagram of a wireless telephone according to the present invention, and FIG. 2 is a circuit diagram of essential parts of the present invention. 9 ...Reception circuit, 28...Audio output control circuit, 29...Intermediate frequency signal detection circuit, 30...Line monitoring circuit, 35 ...Switch circuit.

Claims (1)

[Claims] 1 A base unit connected to a telephone line and a plurality of slave units that communicate wirelessly with the base unit are each provided with a transmitting circuit and a receiving circuit, and the transmitting circuit transmits a carrier wave modulated with a calling signal or a transmit/receive signal, etc. In the receiver circuit that demodulates the carrier wave, switch switches 38 and 39 switch the handset to a standby state in which only the receiver circuit 9 is operated and a communication state in which both the receiver circuit 9 and the transmitter circuit 8 are operated; The receiving circuit 9 includes an intermediate frequency signal detection circuit 29 that detects an intermediate frequency signal, an audio output control circuit 28 that selectively amplifies a calling signal, and the intermediate frequency signal detection circuit 29 and audio output control circuit 28.
a line monitoring circuit 30 that monitors the output signal of the line monitoring circuit 30; a first transistor 31 that is turned on and off by the output signal of the line monitoring circuit 30;
The second transistor 33 and the first transistor 31 are turned on, and after switching the hook switches 38 and 39 to the communication state, the transmission circuit 8 is inactivated even when the switch is switched to the communication state.
39, a switch circuit 35 consisting of a third transistor 32 that continues to supply power supply voltage to the line monitoring circuit 30 is provided, and the switch circuits 38, 3
9 is switched to the standby state, and when the base unit receives a calling signal from the other party via the telephone line, the carrier wave signal modulated by the calling signal and transmitted from the base unit is transmitted to the receiving circuit of the slave unit. 9, an output signal is generated from both the intermediate frequency signal detection circuit 29 and the audio output control circuit 28, so no output is generated from the line monitoring circuit 30, and the first transistor 31 is turned off. When the owner of the handset learns that there is a call by demodulating the carrier wave signal from the base phone and emitting a ring tone from the speaker 27, the handset switch 38, 39 is switched to the communication state. In this state, the calling signal stops and the intermediate frequency signal detection circuit 29 of the receiving circuit 9
Even if the line monitoring circuit 30 generates an output and is supplied to the line monitoring circuit 30, the line monitoring circuit 30 is not supplied with the power supply voltage from the battery 40 via the switch 38, so no output is generated and the communication state is maintained.
When another slave unit is communicating with the base unit in the standby state, when a carrier wave signal is received by the receiving circuit 9 and an output is generated only from the intermediate frequency signal detection circuit 29,
Generates an output from the line monitoring circuit 30, turns on the first transistor 31, thereby controlling the second transistor 33, and switches the switch 38, 39.
Even if the first transistor 31 is mistakenly placed in a communication state, the transmitting circuit 8 remains inoperable, and the first transistor 31
As the transistor 32 turns on, the third transistor 32 also turns on.
Even after the switch switches 38 and 39 are erroneously switched to a communication state, the power supply voltage from the battery 40 is continued to be supplied to the line monitoring circuit 30 in place of the switch switch 39, and the transmitting circuit 8 is kept inoperative. Wireless telephone.