JPH04103231A - Signal changeover device - Google Patents

Abstract

PURPOSE:To prevent the output of an undesired signal at the changeover of a signal subjected to time division by controlling the changeover of a signal changeover circuit before a signal sent in succession to a non-modulation block is received by a switching latch circuit based on a detection signal of the non- modulation block included in a transmission signal. CONSTITUTION:A non-modulation block detection circuit 8 of a receiver side detects a non-modulation block included in a transmission signal from a sender side and a changeover latch circuit 9 based on the detection signal applies changeover control to a signal changeover circuit before a signal sent in succession to the non-modulation block is received. That is, even when an outputted mute signal S3 is stopped after a prescribed time, while a data signal S2 is received, since a mute signal S4 is outputted from a data reception circuit 7, an output of an OR circuit 10 is kept to an H level during that time and a changeover switch 4 keeps the OFF state (voice mute state). Thus, since the data signal S2 is not entirely outputted from an earpiece 6, an event of giving a sense of displeasure to the user on the receiver side is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention provides a method for guiding two or more signals transmitted in a time-divided manner over the same signal transmission path to corresponding signal processing circuits on the receiving side. The present invention relates to a signal switching device.

(Prior Art) An example of a system in which two or more time-divided signals are transmitted over the same signal transmission path is a cordless telephone that transmits a voice signal and a data signal.

That is, in conventional cordless telephones, when it becomes necessary to transmit a data signal during a voice call, the transmitter side switches the voice signal to a data signal and transmits the signal without any warning. Therefore, on the receiving side, either allow the data signal to be output to the audio output at all, or mute the audio when the synchronization signal included in the beginning of the data signal is detected. ing. Furthermore, car telephones and the like employ a method in which a special switching signal is superimposed on the audio signal.

(Problem to be Solved by the Invention) However, allowing data signals to be output as audio outputs causes discomfort to users on the receiving side, and it is also difficult to allow data signals to be output as audio outputs. Even in the method of muting the audio at the same time, a synchronization signal is output to the audio output, which similarly causes discomfort.

In addition, the method of superimposing a special switching signal on the audio signal requires a complicated circuit to separate the switching signal from the audio signal, and also has problems such as using a large number of wireless transmission bands. .

The present invention has been made in view of the above circumstances, and its purpose is to provide an unmodulated portion for a certain period of time between signals continuously transmitted from the transmitting side. An object of the present invention is to provide a signal switching device that can reliably switch transmission signals without using a complicated circuit that separates signals.

(Means for Solving the Problems) In order to solve the above problems, the signal switching device of the present invention transmits two or more time-divided signals on the same signal transmission path, and on the receiving side, the signals are not transmitted. In a signal transmission system equipped with two or more signal processing circuits corresponding to each signal transmitted and a signal switching circuit for guiding each transmitted signal to the corresponding signal processing circuit, continuous transmission is performed from the transmitting side. An unmodulated part for a certain period of time is provided between the incoming signals, and the receiving side includes an unmodulated part detection circuit that detects the unmodulated part included in the transmitted signal from the transmitting side, and A switching holding circuit is provided, which determines that the transmission signal has been switched when the partial detection circuit detects an unmodulated portion included in the transmission signal, and controls switching of the signal switching circuit.

(Operation) In a signal transmission system in which two or more time-divided signals are transmitted over the same signal transmission path, on the transmitting side, a non-modulated part of a certain period of time is provided between the signals to be transmitted. do. On the other hand, on the receiving side, a non-modulated portion detection circuit detects the non-modulated portion included in the transmission signal from the transmitting side, and sends the detected signal to the switching and holding circuit. The switching and holding circuit performs switching control of the signal switching circuit based on this detection signal before receiving the signal transmitted following the non-modulated portion.

(Example) Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is an electrical block diagram showing an example in which the signal switching device of the present invention is applied to a cordless telephone, and shows an example of time-division transmission of analog signals and digital data.

In the figure, an antenna 1 of a handset, which is a telephone terminal, receives a wireless signal from a connection device (not shown), which is a transmitter.
Receiver 2 is connected to , and the output of receiver 2 is
Changeover switch (mute switch) via filter 3
Connected to one terminal of 4. The other terminal of the changeover switch 4 is connected to an earpiece 6 via an amplifier 5.

In addition, the output of the filter 3 is sent to a data receiving circuit 7 for receiving the audio signal and digital data transmitted in a time-division manner, and for detecting a non-modulated portion provided between the audio signal and the digital data. The output of the volume detection circuit 8 is
It is connected to a switching holding circuit 9 that controls switching of the selector switch 4 . Then, the mute output of the switching holding circuit 9 and the mute output of the data receiving circuit 7 are ORed.
connected to each input terminal of the circuit 10, and OR
The output terminal of the circuit 10 is connected to the switching control input of the changeover switch 4.

The selector switch 4 is in the on state when there is no mute output (“H” level signal) from the OR circuit 10, and is switched to the off state when the mute output from the OR circuit IO is given. It looks like this.

FIG. 2 shows an example of a specific circuit configuration of the volume detection circuit 8 and the switching holding circuit 9 described above.

In the figure, the received signal that is the output of the filter 3 is guided to the anode of the diode 81, and
1 cathode is resistor 82, capacitor 83 and resistor 8
It is connected to the non-inverting input terminal of the comparator 86 via a filter circuit consisting of 4. In addition, one end of the inverting input terminal of the comparator 86 is connected to the power supply voltage ■. , and a sliding terminal of a variable resistor 85 whose other end is grounded. The output of the comparator 86 is connected to the trigger input of the one-shot multivibrator 9o, and the Q terminal of the one-shot multivibrator 90 is connected to one input terminal of the OR circuit 10. That is, the one-shot multi-bye break 90 operates for a time length tCR determined by the resistor 91 and the capacitor 92 according to the trigger input.
rH" level pulse is output from the Q terminal.

Next, the operation of the cordless telephone equipped with the signal switching device configured as described above will be explained with reference to the operation timing chart of FIG.

The signal transmitted from the connection device (not shown) is from the third
The audio signal S1 and the data signal S2 are as shown in FIG. ing.

A transmission signal sent from such a connection device side is received by a receiver 2 via an antenna 1, unnecessary components are removed by a filter 3, and then sent to a data receiving circuit 7.
The sound is guided to the volume detection circuit 8, and is sent out as sound from the earpiece 6 via the changeover switch 4 and amplifier 5 which are in the on state. At this time, the data receiving circuit 7 is in an inactive state, no mute signal is output from the mute output, and the changeover switch 4 remains on.

Thereafter, when the unmodulated portion N obtained by muting the audio signal Sl is received at time tl, this signal is rectified by the diode 81 of the volume detection circuit 8, converted to an average volume in the next filter circuit, and then passed through the comparator. 86 non-inverting input terminal. Since the signal at this time is the non-modulated portion N, when the potential of the non-inverting input terminal of the comparator 86 decreases and falls below the set voltage of the inverting input terminal at time t2, the output of the comparator 86 changes from rl to
(A trigger signal of J level is output. The one-shot multivibrator 90 outputs a mute signal S3 having a width of tc+ from the Q terminal in response to this trigger signal. As a result, the output of the OR circuit 10 changes from the "L" level to The signal changes to "H" level, and the selector switch 4 is switched to the OFF state (audio mute state) at time t2 by this "H" level signal. Then, while the mute signal S3 is output from the one-shot multi-vibration break 90. When the synchronization signal Sn included in the head portion of the data signal S2 is received by the data receiving circuit 7, a mute signal S4 is output from the data receiving circuit 7 at time t3. The data will be output until the time when the data runs out.

That is, even if the mute signal 33 output from the one-shot multivibrator 9° stops after a predetermined time,
Since the mute signal S4 continues to be output from the data receiving circuit 7 while the data signal S2 is being received, the output of the OR circuit 10 is kept at the "H" level during this period, and as a result, the changeover switch 4 is also turned off (audio mute state). will be maintained.

With the above configuration, the data signal S2 is not outputted from the earpiece 6 at all, so it is possible to prevent the user on the receiving side from feeling uncomfortable.

In the above embodiment, an example in wireless communication, particularly an example in which the present invention is applied to a cordless telephone, is shown, but the present invention can be similarly applied to wired communication. Furthermore, the type of signals is not limited to transmission of audio signals and data signals (it is also possible to transmit data signals together or audio signals together), and it is also possible to handle three or more types of signals.

(Effects of the Invention) The signal switching device of the present invention provides a non-modulated portion for a certain period of time between signals to be transmitted, and on the receiving side, a non-modulated portion detecting circuit detects the non-modulated portion included in the transmitted signal from the transmitting side. The configuration is such that the non-modulated portion is detected, and based on the detection signal, the switching and holding circuit performs switching control of the signal switching circuit before receiving the signal transmitted following the non-modulated portion. This has the effect that unnecessary signals are not output when switching between signals.

[Brief explanation of drawings]

Fig. 1 is an electrical block diagram showing an example in which the signal switching device of the present invention is applied to a cordless telephone, Fig. 2 is a circuit diagram showing an example of a specific circuit configuration of a volume detection circuit and a switching holding circuit, and Fig. 3 is a flowchart for explaining the operation of the signal switching device. 4... Selector switch 7... Data receiving circuit 8... Volume detecting circuit 9... Switching holding circuit 10... OR circuit No. 21-1

Claims (1)

[Claims] 1) Two or more time-divided signals are transmitted on the same signal transmission path, and on the receiving side, two or more signal processing circuits corresponding to each transmitted signal, and a transmission In a signal transmission system equipped with a signal switching circuit for guiding each incoming signal to a corresponding signal processing circuit, there is a non-modulated part of a certain period of time between signals that are continuously transmitted from the transmitting side. is provided on the receiving side, and includes a non-modulated part detection circuit that detects the non-modulated part included in the transmitted signal from the transmitting side, and a non-modulated part detection circuit that detects the non-modulated part included in the transmitted signal by this non-modulated part detection circuit. A signal switching device comprising: a switching holding circuit that determines that a transmission signal has been switched and controls switching of the signal switching circuit.