JPH0520008B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a system for transmitting signals from a mobile station mounted on a vehicle to a base station to perform wireless communication.

Background Art The prior art will be explained with reference to FIG. A mobile station 1 installed in a car such as a taxi transmits a tone signal at a frequency other than the voice band by operating a press talk switch to identify the company to which the car belongs. In this state, data signals and audio signals are transmitted. The base station 2 and the remote control device 3 on the base station 2 side are installed in a place where radio waves can easily reach, and the base station 2 receives and demodulates a radio signal from the mobile station 1. In the base station 2, when receiving the carrier wave, noise in the demodulated signal is detected by a noise squelch circuit, and when a tone signal included in the demodulated signal is detected by the tone squelch circuit, the demodulated signal is sent to the remote control circuit. 3 through a line 4, such as a telephone line, to a remote control device 5 provided in the company's taxi dispatch center for signal processing and the like.

In general radio equipment (regardless of base station or mobile station), an identification tone signal is detected in the received signal (signal after demodulation), and only when the company's identification tone is detected, The system is such that the speaker circuit is turned on and only the desired sound is heard. When such a radio device is used for a base station and is connected to the remote control devices 3 and 5, the configuration shown in FIG. 4 is obtained if the wireless device is connected as is. That is, the detection of the identification tone signal and the output on/off of the audio signal and data signal are carried out inside the radio, and the signal processing circuits of the remote control devices 3 and 5 are
On/off controlled audio and data signals will be input. With such a configuration, there is no need to transmit the detection result of the identification tone signal to the equidistant controller (slave unit) in the dispatch control room etc. via the base station side remote controller (master unit), and the circuit It has the advantage of having a simple configuration.

Problems to be Solved by the Invention In such prior art, in order to quickly detect a tone signal at the base station 2 and shorten the response time for a data signal, the toe signal resonant circuit included in the tone squelch circuit is Q must be set to a small value. If this is done, there is a risk that signals other than the identification tone signal assigned to the company may be detected, leading to a risk of malfunction. In other words, the identification tone signal detection circuit is a circuit with a very high Q, so when the identification tone signal is detected, the circuit is opened, and the signal is transmitted to the next stage (in this case, the remote controller), the signal is A headache occurs. In other words, even though mobile station 1 is already transmitting voice, data, etc.
On the base station 2 side, a state occurs in which the identification tone signal is not detected and the circuit is not turned on. This head is
This is hardly a problem when only voice calls are being made, but it becomes a major problem when efficient data transmission is desired.

An object of the present invention is to provide a communication system that improves response speed and prevents malfunctions.

Means for Solving the Problems The present invention provides a base station that receives and demodulates a radio signal modulated by a voice signal or data signal from a mobile station and an identification tone signal having a frequency other than the voice band; a remote control device provided at a location away from the base station and comprising a signal processing circuit that receives a demodulated signal from the base station and processes the signal; and a speaker that reproduces the demodulated signal from the base station. In the communication system, the base station is provided with a tone detection means for detecting a tone signal for identifying a mobile station, the remote control device is provided with a control switch for controlling a demodulated signal to be supplied to a speaker, and the tone detection means is provided in the base station. A control means is provided for making the control switch conductive only when a tone is being detected by the means, and the signal processing circuit is provided with a demodulated signal without going through the control switch. It is a communication method.

Effects According to the present invention, a base station demodulates a radio signal, and the demodulated signal includes a voice signal or a data signal and an identification tone signal having a frequency outside the voice band.

This demodulated signal is applied to the speaker via a control switch, which is conductive only when detecting a tone signal. Therefore, an audio signal is generated from the speaker only when a tone signal is received, and is not audible when no tone signal is detected. Acousticization is thus possible only when a specific tone signal is being generated.

In addition, the demodulated signal is given to the signal processing circuit without going through a control switch, which increases the Q of the tone detection means, thereby reducing malfunctions and making it possible to perform efficient data transmission. become.

Embodiment FIG. 1 is an overall electrical circuit diagram of an embodiment of the present invention. Each vehicle, such as a taxi, is equipped with a mobile station 7. The mobile station 7 is equipped with a pre-talk switch, and by operating the pre-talk switch, the tone signal shown in FIG. 2 is generated. After the press talk switch is operated, a data signal is sent out after a time W1 has elapsed, as shown in FIG. 2, and then an audio signal is sent out. For example, the time W1 is 100~
200 msec, and the data signal transmission period is, for example, 100 to 200 msec. The tone signal is constantly generated during operation of the pre-talk switch. These tone signals, data signals, voice signals, and the like undergo frequency modulation of carrier waves, and the radio signals obtained in this way are received by the receiving circuit 9 at the base station 8. Receiving circuit 9 derives a demodulated signal on line 10. This demodulated signal is applied from the switch 11 to the line 13 of the remote control device 12 on the base station 8 side. The base station 8 and the remote control device 12 are installed at a high place where the wireless signal from the mobile station 7 can easily reach. The noise squelch circuit 14 responds to the demodulated signal on line 10, and when the receiving circuit 9 is receiving a radio signal, the noise squelch circuit 14 responds to the demodulated signal on line 10 and
Deriving a low level signal that is the ground level,
This makes the switch 11 conductive. The tone squelch circuit 16 receives the demodulated signal on the line 10 and outputs a high level signal to the line 17 when a tone signal is detected. This tone squelch circuit 16 has a resonant circuit that resonates with a tone signal having a specific frequency, and this resonant circuit has a large Q, thereby preventing malfunctions. The tone signal is, for example, 67.0~
It has a frequency of 250.3Hz. The data signal is
For example, 1200-1800Hz. The audio signal is, for example, 300Hz to 3KHz.

In the remote control device 12 on the base station 8 side, the base station 8
The demodulated signal from the primary winding 19 of the transformer 18
given to. The transformer 18 has two secondary windings 2
It has 0.21. One of the secondary windings 21 is applied from a diode 22 to a receiver element 24 realized by a phototransistor of a photocoupler 23 or the like. The photocoupler 23 includes a light emitting element 25 such as a light emitting diode. This light emitting diode 2
5 is connected in series with the resistor 26, and the lines 15,
Connected between 17 and 17. Secondary winding 2 of transformer 18
A pair of transmission lines 27 and 28, such as telephone lines, connected in connection with 0 and 21 are connected to a remote control device 29 for signal processing provided in a company's dispatch control room or the like.

In the remote control device 29 for signal processing, the lines 27, 28 are connected to the transformer 30 primary windings 31, 32.
connected to. One primary winding 31 has a resistor 33
grounded via. A positive voltage is applied to the other primary winding 32 via resistors 34 and 35, and a Zener diode 36 and a diode 37 output in the opposite direction. A connection point between the resistors 34 and 35 is connected to the base of a switching transistor 38. The signal from the secondary winding 39 of the transformer 30 is connected to an amplifier circuit 40 and is provided from a line 41 to a signal processing circuit 42 . The signal processing circuit 42 processes the data signal and displays it on the display circuit 43. The signal from line 41 is also provided via control switch 44 to speaker 45 to amplify the audio signal. This control switch 44 causes the transistor 38 to conduct and a high level signal to the line 46.
Conducts when given from. transformer 18
A capacitor 47 is connected to the secondary windings 20 and 21 of the transformer 30, and a capacitor 48 is connected to the primary windings 31 and 32 of the transformer 30. In this way, even if the light receiving element 24 of the photocoupler 23 is cut off, data will be transmitted from the remote control device 12 to the remote control device 29 via the lines 27 and 28 as long as the switch 11 is conductive.

When a radio signal is transmitted from the mobile station 7, the radio signal is received and demodulated by the receiving circuit 9 of the base station 8, and the demodulated signal is derived from the line 10. The noise squelch circuit 14 is connected to the line 10.
When a demodulated signal is derived from the signal, the line 15 is set to a low level and the switch 11 is made conductive. For this purpose, data signals are applied to the remote control device 29 via lines 27 and 28, processed in a signal processing circuit 42, and the results of the processing are displayed on a display circuit 43. When the tone squelch circuit 16 detects that a tone signal indicating that a vehicle such as a taxi equipped with the mobile station 7 is owned by the company, the line 17 is set to a high level. As a result, in the remote control device 12 on the base station 8 side, the light emitting element 25 of the photocoupler 23 emits light. Therefore, the light receiving element 24 becomes conductive. The current therefore flows through the resistor 3 in the remote control device 29 for signal processing.
4, 35, broken down Zener diode 36, diode 37, primary winding 32 of transformer 30, line 28, secondary winding 2 of transformer 18
1, diode 22, light receiving element 24, transformer 1
A direct current flows through the secondary winding 20 of the transformer 8, the line 27, the primary winding 31 of the transformer 30, and the resistor 33. This direct current continues to flow while the tone signal is being detected by the tone squelch circuit 16. This causes transistor 38
is conductive, and the control switch 44 is conductive. Therefore, the audio signal from the secondary winding 39 of the transformer 30 is converted into sound by the speaker 45. The data signal from the secondary winding 39 of the transformer 30 is applied to the signal processing circuit 42 for signal processing as described above, and its contents are displayed by the display circuit 43.

In the above-described embodiment, the Q of the resonance circuit for detecting a tone signal of a specific frequency in the tone squelch circuit 16 is set to a large value, thereby making it possible to accurately detect the tone signal. Prior to detecting the tone signal, the switch 11 becomes conductive, thereby sending the data signal through the lines 27 and 28 to the remote control device 29 for signal processing for high-speed signal processing. becomes possible.

FIG. 3 shows a timing chart when data signals and voice signals are transmitted from the mobile station 7 and received by the base station 8. In the embodiment shown in FIG. 1 described above, the switch 11 is controlled to open and close by the output of the noise squelch circuit 14, and
is controlled to open and close by the output of the toe squelch circuit 16. As a result, audio can be heard from the speaker 45 only when the identification tone signal is detected.In other words, the audio signals of other companies that use the same frequency and other identification tone signals are not output from the speaker 45, and the Only the voice of the mobile station 7 can be heard. This is the same as the original usage of the identification tone signal. On the other hand, the data signal is opened and closed only by the noise squelch switch 11 and does not pass through the tone squelch switch 44. Therefore, processing can be performed quickly regardless of the delay in the tone detection operation. Generally, the response speed of noise squelch is sufficiently faster than that of tone squelch. Normally, the data signal includes an identification pattern that indicates that it is the company's data, so there is no risk of problems even if it is processed independently of the identification tone signal.

In this way, by providing the switch 44 that opens and closes with a tone squelch in the slave unit that is the remote control device 29, and handling data and voice at different timings, identification tone detection with high Q, that is, with fewer malfunctions, is possible. It becomes possible to perform efficient data transmission using this method.

Effects As described above, according to the present invention, a communication system that reduces response time and prevents malfunctions is realized.

[Brief explanation of the drawing]

Fig. 1 is an electrical circuit diagram of an embodiment of the present invention;
3 is a diagram showing the structure of a signal from the mobile station 7, FIG. 3 is a time chart for explaining the operation in the embodiment shown in FIGS. 1 and 2, and FIG. 4 is a diagram for explaining the prior art. FIG. 7... Mobile station, 8... Base station, 9... Receiving circuit, 11... Switch, 12, 29... Remote control device, 14... Noise squelch circuit, 16... Tone squelch circuit, 18, 30... Trance, 2
3...Photocoupler, 42...Signal processing circuit, 43
... Display circuit, 44 ... Control switch, 45 ...
speaker.

Claims (1)

[Claims] 1. A base station that receives and demodulates a radio signal modulated by a voice signal or data signal from a mobile station and an identification tone signal having a frequency other than the voice band; In a communication system, the remote control device includes a signal processing circuit that is installed at a location and performs signal processing upon receiving a demodulated signal from the base station, and a speaker that reproduces the demodulated signal from the base station, The base station is provided with tone detection means for detecting a tone signal for identifying a mobile station, the remote control device is provided with a control switch for controlling a demodulated signal to be supplied to a speaker, and the tone detection means detects a tone. 1. A communication system, characterized in that a control means is provided for making the control switch conductive only when the signal processing circuit is in a state where the signal processing circuit is in a state where the signal processing circuit is in a state where the signal processing circuit is in a state where the signal processing circuit is in a state where the signal processing circuit is in a state where the signal processing circuit is in a state where the signal processing circuit is in a state where the signal processing circuit is in a state where the signal processing circuit is in a state where the signal processing circuit is in a state where the signal processing circuit is in a state where the signal processing circuit is in a state where the signal processing circuit is in a state where the signal processing circuit is connected to the signal processing circuit.