JPS6322102B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides information signal sounds that are mixed into received audio during standby reception in a communication system that performs calls and data transmission by inserting audio frequency information signals such as FSK signals between audio signals. The present invention relates to a device for removing.

Control signals that are sequentially inserted into the call tone can cause significant discomfort to the operator on the called side if the control signals are inserted frequently. Therefore, it is desirable to prevent the control signal from being input to the speaker, but
When the occupied bandwidth is wide and the carrier frequency is set near the center of the audio signal band, such as an FSK signal, suppressing the information signal using a band rejection filter (BEF) is difficult to apply because the sound quality of the call deteriorates. Furthermore, if the audio signal transmission system is blocked by information signal detection by a bandpass filter (BPF) and its detection output, there is a risk of malfunction or partial leakage of the information signal. In other words, since the audio signal is also in the same frequency band, it is necessary to take time to thoroughly check the signal structure in order to detect the information signal. However, in this case, the leading part of the signal is directed toward the speaker before it is determined to be an information signal. It flows away. If detection is accelerated to avoid this, there is a risk that the audio signal will be mistaken for an information signal.

The present invention addresses such problems and includes:
Its features include a circuit for detecting the audio frequency information signal in an information signal sound removal device for a communication system that performs phone calls and data transmission by inserting an audio frequency information signal such as an FSK signal between audio signals; A circuit for delaying the received signal and an electroacoustic transducer driving circuit on the output side of the delay circuit, and the state changes in response to the output of the detection circuit to input the information signal to the electroacoustic transducer. An analog switch is provided to prevent this. With this method, there is no risk of malfunction or partial leakage.
Furthermore, a detector for bit synchronization signals, frame synchronization signals, etc. provided in the signal receiving system can be used to detect this information signal, and there is an advantage that no special circuit components are required. Next, this will be explained in detail with reference to examples.

FIG. 1 shows a portion for removing information signals in an embodiment of the present invention, where RS is a received signal consisting of a call voice or an FSK digital information signal. Chain line frame 1
0 is an FSK signal receiving section, which includes an FM demodulator 12, a serial-parallel converter 14, a synchronization pattern detection circuit 16,
Consists of others. 20 is a signal delay circuit provided in the audio receiving system, 22 is an analog switch, 24 is a timer that generates an opening/closing signal for the switch, and 26 is an amplifier for driving the speaker 28. As shown in FIG. 2, the FSK signal consists of a prefix signal, a bit synchronization signal, a frame synchronization signal, and a data signal, and the prefix signal continues at 1300 Hz for 200 mS. However, due to the rising characteristics of the transmission line, the front part of the received wave may be partially missing. Each bit sync, frame sync and data signal is 200 bits/
sec, mark 1100Hz, space 1300Hz FSK signal, and the bit synchronization signal is 32 bits (160m
S), the frame synchronization signal consists of 15 bits (75 mS), and the data signal consists of 64 bits (320 mS). Therefore, the time length _T1 occupied by the prefix, bit synchronization, and frame synchronization signals is 435 mS, and the total time length including the data signal is 755 mS. In accordance with these times, the delay time of the signal delay circuit 20 is set to 440 mS, and the output time of the switch open signal of the cutoff signal generation timer 24 is set to 760 mS.

In this device, if the received signal RS is audio, it enters the speaker 28 via a signal delay circuit 20, an analog switch 22, and an amplifier 26, and drives it. If it is an FSK signal, it enters the receiving section 10,
It is demodulated by the FM demodulator 12 and becomes binary serial information of "1" and "0", which is then sent to the serial-to-parallel converter 14 consisting of a shift register and a gate circuit.
It enters a synchronization pattern detection circuit 16 to detect a frame synchronization signal, and on the other hand enters a circuit (not shown) to extract a bit synchronization signal, assemble data bits, etc., and demodulate it. The data signal is used for various purposes such as control. However, with conventional devices of this type,
Since FSK signal is an audible sound of 1.1 or 1.3KHz
The FSK signal not only goes into the receiver, but also goes into the amplifier and speaker, causing it to ring, which is extremely annoying to the operator. Therefore, in the present invention, an analog switch 22 is provided, which is turned off when receiving the FSK signal. FSK signal reception detection can also be performed using a filter BPF and a positive polarity diode D ₁ , a filter BEF and a reverse polarity diode D ₂ , and a circuit MIX that combines the outputs of these systems, as shown in FIG. In other words, when the received signal RS enters the input terminal, it passes through the filter BPF that passes 1.1 to 1.3KHz, is detected by the diode _D1 , and becomes a positive output + _O1 , and then passes through the filter BEF that blocks 1.1 to 1.3KHz.
is detected by diode D ₂ and outputs negative output −O ₂
The synthesizer calculates +O ₁ - O ₂ and extracts it from the output terminal, but if the received signal RS is an FSK signal, most of the signal energy is 1.1~
Since it is within 1.3KHz, positive output + O ₁ only and negative output -
Although there is no O ₂ , since the audio signal extends over a range of 300 to 3000 Hz, there are positive and negative outputs +O ₁ -O ₂ , and their combined value is smaller than when +O ₁ is used alone.
Therefore, by detecting the H and L levels of the output of this synthesizer MIX, it is possible to identify whether it is a voice or an FSK signal. However, the FSK demodulator 10 is provided with a synchronization pattern detection circuit 16, etc., and this output is
Since this shows FSK reception, it is easier to use this than to use a circuit like the one shown in FIG. However, as is clear from FIG. 2, the frame synchronization signal is detected after more than T ₁ =435 mS has elapsed since the signal was received, and until then the switch 22 is open, so the signal passes through and is emitted from the speaker. Therefore, a circuit 20 that provides a delay slightly larger than T ₁ is provided, and a timer 24 that outputs a time that is slightly longer than the total length of the FSK signal is provided. It is triggered by the output and causes the analog switch 22 to output an open signal. In this way, FSK
It is possible to reliably block the signal from its start end to its end, so that no sound is emitted from the speaker.

If the signal delay circuit 20 is inserted, the audio signal will naturally also be delayed by 440 mS. Although this is not a particular problem during standby and reception, it cannot be ignored when making a call (this communication system is used, for example, for taxi radio, and during a call refers to when issuing a dispatch order, etc., but when the delay circuit 20 is inserted, the response cannot be ignored. (It won't go smoothly). FIG. 3 is a diagram showing an entire embodiment of the present invention in which this point has been improved, and the delay circuit system is cut off during a call, and a non-delayed reception signal is provided to the speaker. 40 is an analog switch added for this purpose, which leads the received signal RS directly to the amplifier 26. 32 is a circuit for detecting a received signal;
34 is a timer circuit which receives the output pulse of the circuit 32 at the end of the received signal and generates an output for 2 seconds;
6 is a differentiator circuit that generates a pulse at the trailing edge of the output of the circuit 34. Further, 38 is a transmission signal detection circuit that generates an output pulse when the pre-talk control signal PCS, which is turned on when transmitting a call, is no longer present, and 42 is a circuit 38.
44 is a differentiator circuit that generates a pulse at the trailing edge of the output of circuit 42, 46 is an OR circuit, and 50 is a timer circuit that generates an output for 10 seconds in response to the output of the received signal detection circuit 32. The output, the output of the transmission signal detection circuit 38, and the output of the flip-flop 48 are input, and the flip-flop 48
When the output of flip-flop 48 is H, the logical sum of the output of the received signal detection circuit 32 and the output of the timer circuit 34 and the output of the transmitted signal detection circuit 38 is output, and when the output of the flip-flop 48 is low, the transmitted signal is detected. This is a logic circuit that transmits only the output of the circuit 38. Flip-flop 48 is set by the output of OR circuit 46 and reset by the output of logic circuit 50, with its Q output turning on analog switch 22 and its output turning on analog switch 40.

In this circuit, the press talk control signal is used when transmitting.
The PCS is turned on, which turns off the analog switches 22 and 40, and the input circuit of the amplifier 26 is cut off, so that no sound is emitted from the speaker 28. When the transmission ends and the signal PCS disappears, switch 2
The off control of PCS 2,40 is released and circuit 38 produces an output which, via logic circuit 50, resets flip-flop 48, which turns on analog switch 40.
Therefore, when there is a response from the other station, this received signal
The RS (audio) does not pass through the delay circuit 20, but directly enters the amplifier 26 from the switch 40 and is emitted from the speaker 28. A response to this response is made by turning on the signal PCS, thus allowing communication with the other station to be made quickly without delay. Signal PCS when entering standby
will not turn on, so circuit 3 occurs when the PCS is turned off.
Flip-flop 4 enters output 42 of 8 and after 10 seconds
8, set the Q output to H level, turn on switch 22, and turn off switch 40. Therefore, the reception signal RS in the waiting state is transmitted to the signal delay circuit 20, the receiving section 10,
The sound is emitted from the speaker 28 by the above-mentioned operation by the timer 24 and the switch 22, but the FSK
The signal is blocked. Note that when a received signal is detected by the circuit 32 during the above 10 seconds, the output of the received signal detection circuit 32 is reset while the received signal continues, and the output of the timer circuit 24 is reset of the slip-flop circuit 48 for 2 seconds after the received signal disappears. Since the (R) terminal is continuously held at H, the output of the differentiating circuit 44 applied to the set (S) terminal of the flip-flop circuit 48 becomes invalid, and when the output of the timer circuit 34 disappears, the output of the differentiating circuit 36 is generated. It is set by the pulse output.

As described above, during standby, the delayed signal is selected and the information signal tone is removed, and during talk, the received signal that arrives within 10 seconds after the end of the call is reproduced without delay.
If the receiving state does not end within the above 10 seconds, the non-delayed reception time is extended until 2 seconds after the end of receiving the call, and if it ends within a short time, the non-delayed reception time is disabled 2 seconds after the end of receiving the call, regardless of the 10 seconds. Abort delayed reception.
Note that if reception is resumed within 2 seconds after the end of reception, the operation will be the same as when the call is continuing. This two second time lag is provided to prevent unnatural switching at breaks in speech or sentences. In this example, when transmitting a call, both analog switches 22 and 40 are opened to cut off the receiving sound, but it is also possible to transmit and receive calls at the same time if the analog switch 22 is modified to turn off only the analog switch 22, depending on the purpose. . The analog switch in this example is connected to the input side of the speaker drive amplifier so that the signal path is broken when it is opened, but it should be noted that other connections may be used as long as the same reproduction sound is obtained. Not even.

Furthermore, in the audio frequency information signal of this example, if a bit synchronization circuit is used as a detection circuit for the signal, audio malfunctions will increase slightly, so a frame synchronization circuit is used, but the signal length and frequency of the bit synchronization signal are different from this example. However, it goes without saying that a bit synchronization circuit can be used if there is no risk of malfunction. In this example, a part of the transmission line uses a mobile radio line where the transmission quality sometimes deteriorates extremely, so a prefix signal is placed at the start of the signal to improve the reliability of the bit synchronization circuit operation. This signal can be omitted if the line is always in good condition.

The bit synchronization signal is a signal for transmitting read timing information of the serial signal, and can be omitted if the subsequent serial signal is of a coding system including read timing information (for example, start-stop synchronization). The frame synchronization signal is a signal for transmitting starting point information of a data signal, and can be omitted if the starting point information is transmitted by another method (for example, start-stop synchronization). Even in the case of only a data signal, if the modulation signal array of the audio frequency information signal is set so that it can be distinguished from the audio signal, the information signal detection circuit can be configured not only by the method shown in FIG. 4 but also by a coincidence detection circuit. Although the code in this example is an NRZ equal-length code and the subcarrier modulation method is FSK, other methods may be used for both the code and the modulation method. As described above, even if the format of the audio frequency information signal is different from this example, the present invention can be achieved by detecting a portion that can be distinguished from an audio signal based on the arrangement of modulated signals of the information signal and outputting the information signal detection. is possible.

As described in detail above, according to the present invention, the user does not have to worry about FSK signal sound while on standby, can communicate quickly, and has the advantage of having a simple circuit configuration.

[Brief explanation of the drawing]

1 and 3 are block diagrams showing embodiments of the present invention, FIG. 2 is an explanatory diagram showing the format of an FSK signal, and FIG. 4 is a block diagram showing an example of an FSK signal detection circuit. In the drawing, 16 is an audio frequency information signal detection circuit, 20
2 is a signal delay circuit, and 22 is an analog switch.

Claims (1)

[Claims] 1 In a system that performs phone calls and data transmission by inserting audible frequency information signals such as FSK signals between audio signals, an electroacoustic transducer that converts the audio signal into audio, and an electroacoustic transducer that converts the audio signal into audio according to the input signal. an electroacoustic transducer drive circuit that drives the
A first switch that transmits the received signal to the electroacoustic transducer drive circuit, which has a delay circuit that delays the received signal and a first switch that conducts or interrupts transmission of the received signal.
a second transmission line that transmits the received signal to the electroacoustic transducer drive circuit, and a second switch that conducts or cuts off the transmission of the received signal; Judgment means comprising a frequency information signal detection means, a received signal detection means and a transmitted signal detection means, and determines whether a call is in progress or a call is on standby based on the detection outputs of the received signal detection means and the transmitted signal detection means. , timer means for shutting off the first switch when an audio frequency information signal is detected by the detected audio frequency information signal detection means; and timer means for shutting off the first switch when it is determined that a call is in progress by the determining means. and a logic means for making the second switch conductive, and prevents input of the information signal to the electroacoustic transducer during a call, and does not delay the received signal during a call. An information signal sound removal device characterized in that the information signal is transmitted to the electroacoustic transducer.