JPS6347174B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting a failure in a slave station at a master station in a communication system comprising a master station and a plurality of slave stations.

In order to maximize the functionality of a system that has a large number of slave stations scattered throughout the country, such as the disaster prevention administrative radio system set up in preparation for emergencies, it is necessary to detect failures of a large number of slave stations as early as possible. It is very effective to detect and take countermeasures.

For this reason, conventionally, a master station calls each slave station one by one, and the slave station that receives the call sends a signal indicating whether it is normal or abnormal. An abnormality was detected.

However, according to the conventional detection method, the ringing time becomes long because a ringing signal must be sent to each station one by one, and when the number of slave stations increases, the call interference time during which the call is interrupted due to failure detection becomes very long. In addition, it requires an oscillator for generating normal and abnormal signals in a large number of slave stations, which has the disadvantage of being expensive.

As an improvement over these shortcomings, only one type of normal signal is used, the master station calls all slave stations at the same time, and the slave stations automatically receive the normal signal after a set period of time has elapsed. A transmission method has been proposed. According to this system, the ringing time is significantly reduced, so the call interruption time is shortened. Further, a slave station to which a signal is transmitted is normal, and a slave station to which a signal is not transmitted can be detected as a failure.

However, according to the above-mentioned improved conventional fault detection method, a fault cannot be detected unless the slave station is in a complete fault state, such as when the transmission output becomes almost zero or when the battery of the power supply unit stops discharging. I can't do it.
Further, since the transmission from the slave station is only carried out for a short time, if the master station is experiencing short-term reception interference due to noise or the like when transmitting a signal from the slave station, the signal from the slave station will not be received. Therefore, it is not possible to detect an abnormal operating state before it becomes a complete failure state and prevent the failure by early maintenance, and even if the slave station is normal, it may be determined to be a failure. It had certain drawbacks.

Therefore, an object of the present invention is to enable the master station to detect the normal and abnormal operating states of the slave station without installing a new oscillator in the slave station, and to enable the master station to detect the normal and abnormal operating states of the slave station reliably even if the master station is subject to short-term reception interference. An object of the present invention is to provide a failure detection method that can perform accurate failure detection.

In order to achieve such an objective, the present invention focuses on the fact that in a disaster prevention administrative radio system, a slave station transmits a calling signal when communication starts, and a call termination signal having a frequency different from the calling signal when communication ends. death,
This is used as a confirmation signal to indicate whether the slave station is normal or abnormal. That is, when the slave station is normal, a calling signal is repeatedly transmitted, and when the slave station is abnormal, a call termination signal is repeatedly transmitted, and the master station receives this and determines whether the slave station is normal or abnormal. The failure detection method according to the present invention will be explained in detail below using the drawings.

FIG. 1 is a block diagram of a slave station showing an embodiment of the present invention, in which the input end of a signal detection circuit 2 is branch-connected to the demodulation output line connected to the demodulation output terminal 1a of the transceiver 1. ing. The signal detection circuit 2 uses a buffer amplifier internally to prevent the effects of connecting the signal detection circuit 2 from appearing on the demodulation output line, and prevents the lock signal, test signal, and synchronization signal sent from the master station from appearing on the demodulation output line. , the recovery signal is received, and output signals of logic level are sent out from the output terminals 2a to 2d, respectively. 3 is a control circuit, and input terminals 3a to 3
3a to 3d of e are the output terminals 2 of the signal detection circuit 2
3e is connected to the output end of the alarm detection circuit 4. And control circuit 3
Of the output terminals 3f to 3h, the output terminals 3f and 3g are connected to the input terminals of a call signal generator 5 used as a normal signal generator and a call termination signal generator 6 used as an abnormal signal generator, respectively. An output end 3h of the circuit 3 is connected to an input end 7a of the switching circuit 7.
The output terminals of the call signal generator 5 and the call termination signal generator 6 are both connected to the input terminal 7b of the switching circuit 7,
A signal line for a modulated signal for telephone calls is connected to the remaining input terminal 7c of the switching circuit 7. The output terminal 7d of the switching circuit 7 is connected to the modulation input terminal 1b of the transceiver 1, and the alarm detection circuit 4 has input terminals 4a to 4d.
are connected to the alarm signal output terminals 1c and 1d of the alarm detection circuit 4 to detect a decrease in transmission output and a decrease in receiver limiter current, and are connected to the other input terminals 4c and 4d of the alarm detection circuit 4, respectively.
is connected to a power supply device (not shown) to detect and output a drop in power supply voltage, a drop in the liquid level of the storage battery, etc. The control circuit 3 receives the logic level lock signal, test signal, and synchronization signal detected by the signal detection circuit 2, operates the switching circuit after a pre-allocated time has elapsed, and outputs the alarm detection circuit 4. When there is no output signal, the call termination signal generator 6 is driven, and when there is no output signal, the call signal generator 5 is driven. On the other hand, the master station is equipped with a display device (not shown) that transmits and receives signals with the slave stations and displays whether the slave stations are normal or abnormal.

The operation of the failure detection system according to the present invention configured as described above is as follows. Signal transmission and reception between the master station and the slave stations are performed in the order shown in the time chart in Figure 2, where I to H are the master station, H and G are slave stations A, CH and LI are slave stations B, and N and R are slave stations. The operation of slave station C is shown. During the test, the ground signal shown in Figure 2A is given to the master station, and this ground signal continues during the fault detection period. When the master station receives the earth signal, it briefly transmits to all slave stations a lock signal a which prohibits the slave stations from talking, a test signal b, and a synchronization signal c which is a reference for transmitting a confirmation signal, respectively, in this order. Then, at slave stations A to N,
As shown in the figure below, this signal is received by each station at the same time. The received signals are detected by the signal detection circuit 2 shown in FIG. 1 and supplied to the input terminals 3a to 3c of the control circuit 3. The operations up to this point are performed simultaneously by all slave stations A to C.

When the slave station A receives the three types of signals, the control circuit 3 automatically controls the switching circuit 7 to switch between the input terminal 7b and the output terminal 7d of the switching circuit 7 after a predetermined time elapses for the slave station A. Connect. Child station A
Since no output signal is sent from the alarm detection circuit ₄ when there is no abnormality in Transmit a calling signal for a short time as shown. The master station receives this signal as shown in E, detects from the frequency of the received signal that it is a calling signal indicating that the slave station is normal, and displays the slave station A on a display device (not shown) as shown in B. Normal display is performed.

When the slave station B receives the three types of signals, the slave station B performs the same operation as the slave station A after a predetermined time has elapsed. Alarm detection circuit 4 of slave station B
If the alarm detecting circuit 4 detects some kind of failure, for example, a drop in the battery liquid level, the alarm detection circuit 4 sends an output signal to the control circuit 3. Therefore, the control circuit 3 controls the switching circuit 7 and simultaneously outputs the call termination signal generator 6.
and transmits a call termination signal for a short period of time as shown by _e1 in Figure 2. The master station receives this signal as shown in E, detects from the frequency of the signal that it is a call-end signal indicating an abnormality in the slave station, and displays the abnormality in slave station B on the display device (not shown) as shown in C. Perform display.

As described above, slave station A receives a call from the master station.
~C sequentially transmits a call signal indicating a normal state or a call termination signal indicating an abnormal state, and the master station sends a call signal indicating a normal state or a call termination signal indicating an abnormal state, and the master station sends a call signal indicating a normal state or a call termination signal indicating an abnormal state.
Displays normal or abnormal status. Since the transmission of the confirmation signal from the slave station is for a short time, the master station may not be able to receive this confirmation signal if the master station has received interference such as noise. For this purpose, the control circuit 3 in the slave station controls the confirmation signal to be transmitted at regular time intervals to ensure that the confirmation signal is received at the master station. For example, regarding slave station A, d ₁ and d ₂ in FIG. 2 show a state in which confirmation signals are repeatedly transmitted.

When the master station finishes checking the operation status of the slave stations, it sends out a recovery signal as shown in g in Figure 2D, so all slave stations receive this recovery signal at the same time and restore the status before the test. to stop sending the confirmation signal.

As described above, according to the present invention, the signal for identifying the normal state and abnormal state of the slave station is used as the call origination signal and the call termination signal for controlling the connection of the call.
It is possible to detect the status or abnormality of a slave station without installing a new oscillator. Furthermore, by automatically repeatedly transmitting the confirmation signal from the slave station, reception at the master station can be ensured. Since the call origination signal and the end-of-call signal are used together, it goes without saying that the master station is configured so that the outgoing call signal is not used for call origination processing and the end-of-call signal is not used for end-of-call processing during the test period.

Note that in this embodiment, the tone signal was explained, but
It can also be an FSK signal or a combination of an FSK signal and a tone signal. Further, although the description has been given as disaster prevention administrative radio, the present invention is not limited to disaster prevention administrative radio as long as it is a communication system that uses a calling signal for controlling connection of a call and a call termination signal of a different frequency.

As explained above, according to the fault detection method according to the present invention, the slave station receives a test signal from the master station, and after a predetermined time has elapsed, the slave station changes the frequency corresponding to the normal or abnormal state of the slave station. Two different confirmation signals are sent repeatedly until a recovery signal is received from the master station.This confirmation signal also serves as a call signal and a call termination signal, so it is possible to send a new confirmation signal to a slave station with a large number of stations. This has an excellent effect of being able to reliably detect whether the slave station is normal or abnormal in a short time without the need for a separate oscillator.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a slave station showing an embodiment of the failure detection method according to the present invention, and FIG. 2 is a time chart showing the timing of signal transmission and reception between the master station and the slave station. 1...Transmitter/receiver, 2...Signal detection circuit, 3...
Control circuit, 4... Alarm detection circuit, 5... Normal signal generator, 6... Abnormal signal generator, 7... Switching circuit.

Claims (1)

[Claims] 1 In a communication system consisting of a master station and a plurality of slave stations, the slave stations transmit a call signal for a short time at the start of communication, and at the end of communication transmit a call termination signal with a frequency different from that of the call signal. A slave station that receives a common test signal that is sent to all slave stations at the same time will send a calling signal if the slave station is operating normally, or after a time allotted to each slave station in advance, if the slave station is operating normally, or if it is operating abnormally. A fault detection method characterized by repeatedly transmitting a call termination signal for a short period of time until a recovery signal is received from the master station.