JPS6237574B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a line signal scanning system, and more particularly to a line signal scanning system used in multiple access radio telephone equipment such as a rural telephone system.

Typically, multiple access radiotelephone equipment
It is configured as shown in the figure. As shown in the figure, a master station 1 connects a subscriber line exchange 2 to a connection control device 4 through subscriber lines 3 equal to the number of subscribers (for example, 60 lines).
connected to. This device 4 has a line concentration function and is connected to the same number of wireless devices 6 as the connection lines 5 (for example, 6 lines) in which subscriber lines are concentrated, and from this wireless device 6 via an antenna duplexer 7 Connected to antenna 8. On the other hand, slave stations 11a-1
1n is equal to the number of subscribers, and for example, in this example, there are 60 units from No. 1 to No. 60. These slave stations 11a to 11n are in a state of receiving idle line signals from the master station, except for those that are talking to the master station.
When called by the master station, it occupies the air channel, establishes a wireless link, and enters a talking state.

The system shown in FIG. 1 shows a communication method (multi-channel multi-party communication method) in which a plurality of wireless lines (6 lines) are jointly used by a plurality of subscribers (60 stations). In this multi-channel multi-party communication system, there is the following equation as a connection control method for establishing a wireless link between a master station and a specific slave station.

That is, the master station designates one of the unused free wireless lines as a control channel for exchanging connection control signals with the slave station. Then, the master station transmits a signal to notify the slave station that the corresponding free wireless line is the current control channel. This signal is called a blank line signal.

On the other hand, among the slave stations, those that are not communicating and are in a standby state search for a wireless line that is transmitting an idle line signal and stop there. A slave station requesting a call transmits a call signal to the master station via the wireless line through which the idle signal is sent. When the master station receives the calling signal from the corresponding slave station, it stops transmitting the idle signal. When other slave stations waiting on the wireless line on which the idle line signal is being sent confirm that the idle line signal has stopped and that they do not receive a signal addressed to them even after waiting a certain period of time, they Move away from the line and start searching for the radio circuit where the idle signal is being sent. When a new wireless line is found that is transmitting an idle signal, it stops there and enters a standby state.

On the other hand, when the slave station that issued the call request receives a signal from the master station that acknowledges its own call request, the slave station changes the wireless line on which the idle signal was previously sent to the line for calls or data transmission. Use as. When the communication ends, the slave station abandons the wireless line it was using and begins searching for the wireless line on which the idle signal is being sent. When a wireless line on which a dead line signal is being sent is found, the slave station enters a standby state on that line.

In the case of an incoming call from the master station to the slave station, the master station stops the idle line signal of the wireless line that is transmitting the idle line signal. The master station then sends a signal to call a particular slave station. When the slave station receives the own call signal, it sends a response signal back to the master station. When the master station receives this response signal, it uses the radio line with idle signal stopped as a communication line to call the slave station in order to make a call or transmit data with the slave station. The master station then selects one of the other available wireless lines and sends an idle line signal to it. The slave station that is not the target of the call starts a scanning operation for the idle line signal, searches for a radio line on which the idle line signal is being sent, and then enters a standby state.

The above connection control method is called a circular localization method. In a method that uses this circular localization method,
It is required to quickly and accurately detect idle channels.

SUMMARY OF THE INVENTION An object of the present invention is to provide a blank line signal scanning method that can quickly and accurately detect a blank line channel.

According to the present invention, when forming a mutual communication path between one master station and a slave station to communicate with among a large number of slave stations, one of the plurality of channels is currently used for communication or data transmission. In a system in which an idle line signal is sent to one idle line channel and this idle line channel is used as a mutual signal path, when the idle line signal is being detected, the idle line signal is provided in the signal path leading to the signal receiving circuit. The signal path closing function is stopped and the empty line channel detection system detects the empty line signal for each channel with the minimum time to detect the empty line signal, and the first time is the empty line signal detection operation for all channels. After the second time, the signal is detected only for the channel where the empty line signal was detected last time, and after performing the detection operation a specified number of times, the channel where the empty line signal is detected is determined to be the empty channel. If the idle line signal is detected in only one channel at the first time, the idle line signal component is detected only for that radio line in the second time, and if the idle line signal level is detected again, the idle line signal component is detected for the corresponding radio line. A blank line signal scanning method is characterized in that it is determined that a blank line signal is being sent to a line, and if a blank line signal is not detected in any channel, the first blank line detection is repeated. Suggested.

Hereinafter, an embodiment of the blank line signal scanning method according to the present invention will be described in detail with reference to FIG.

Figure 2 shows a block circuit for searching for a wireless line on which a blank line signal is being sent.
1 is a high frequency circuit, 22 is a mixer, 23 is a high frequency channel selection gate, 24 is an intermediate frequency amplifier, 25
is a discriminator, 26 is an audio amplifier, 27 is a scale circuit, 27a is a noise amplifier,
27b is a diode, 27c is a switch, 27d
28 is a gate, 28 is a signal receiving circuit, 29 is a signal processing circuit and a connection control circuit, and 30 is an empty line signal scanning circuit.

The operation of this blank line signal scanning circuit will now be described.

(1) Steady state If there is a wireless line on which a idle line signal is being sent by the master station, the idle line signal scanning circuit of the slave station enters a standby state on the wireless line on which the idle line signal is detected. ing.

The standby state refers to a state in which a slave station is stopped on a wireless line to which an idle signal is being sent and is detecting the presence or absence of a call request from its own station and an incoming call request addressed to its own station.

In this standby state, the idle line signal scanning circuit
Detecting idle line signals on stopped wireless lines. As long as a blank line signal is detected, it will not move to another wireless line.

If there is no wireless line on which a idle line signal is being sent by the master station, the idle line signal scanning circuit of the slave station transmits the idle line signal while switching the wireless line until a idle line signal is detected. Continue to detect.

(2) Conditions for starting idle line signal scanning (a) Start idle line signal scanning when the power is turned on to search for wireless lines that are transmitting idle line signals.

b. When there is an incoming call from the master station to the slave station, the master station stops transmitting the idle signal and transmits the slave station calling signal.

If the slave station cannot receive the slave station calling signal addressed to itself even after waiting for a certain period of time after detecting that the idle line signal has stopped, it activates the idle line signal scanning circuit and switches the wireless line to the idle line. Find the wireless line that is transmitting the line signal.

C. When the slave station finishes a call and abandons the use of the wireless line it was using, the slave station activates the idle line signal scanning circuit and searches for the wireless line on which the idle line signal is being sent. .

D. A call request is generated to the slave station on which the wireless line to which the idle line signal is being sent is in standby mode, and the call request signal is transmitted to the master station. When the master station receives the call request signal, it stops sending out the idle signal,
Sends a signal to the slave station to permit it to make a call. If the slave station cannot receive this call permission signal, it activates the idle line signal scanning circuit to search for the radio line that is sending out the idle line signal.

(3) How to detect a blank line signal A blank line signal generally consists of a single tone or a double tone. The components of this blank line signal are extracted by a filter provided in the signal receiving circuit 28 shown in FIG.

In the idle line signal scanning circuit as shown in FIG. 2, the signal receiving circuit 28 sends the received signal to the signal processing circuit and connection control circuit 29. This circuit 29 processes signals and performs connection control. The idle line signal scanning circuit 30 is activated by the scan start command sent from the circuit 29, and by sequentially switching channel selection signals, checks whether or not a blank line signal exists in the corresponding channel, and finally To do so, lock onto the empty channel. That is, it sequentially checks for a certain period of time whether or not a blank line signal is being sent to each channel, and locks the blank line signal scanning circuit 30 to the channel in which the blank line signal is detected.

The above is the operation of a slave station that is not communicating with the master station, and all such slave stations are locked to the same idle channel until, for example, a call is made by the master station. When the master station calls a slave station in this state, first the idle signal transmission from the master station is stopped.
When the slave station detects this idle line signal disconnection in the circuit 29, it activates a timer (not shown) and waits for a selection signal sent from the master station for a certain period of time. When a slave station does not receive a selection signal addressed to it within a certain period of time, it activates the idle signal scanning circuit 30 in order to search for another idle channel. On the other hand, in the slave station to which the selection signal addressed to the own station has been sent, the circuit 29
This is detected, the idle line signal scanning circuit 30 is kept locked, and a call is made with the master station.

However, as shown in FIG.
In a system in which a closing function of the audio amplifier 26 is provided by a squelch circuit 27 at the front stage of the squelch circuit 27, the switch 27c of the squelch circuit 27 is provided with a time constant for stable operation. delay by a minute. This causes a delay in the squelch circuit 27, and it is necessary to set the channel scanning time longer. In particular, when switching from a channel where noise was detected to a channel where an idle signal is being sent, the discriminator 25
Even though the output of the audio amplifier 26 includes a blank line signal, the blank line signal is not outputted from the audio amplifier 26 during the delay time. This will have a negative effect on the idle channel detection operation.

Therefore, in the present invention, the blank line signal scanning circuit 30
When the SQ inhibit signal is being searched for a channel with a blank line signal from a large number of channels, the SQ inhibit signal is sent to the squelch circuit 2 via the inhibit gate 27d.
7 and prohibits the squelch circuit 27 from closing the signal path so that the signal receiving circuit 28 can quickly detect the idle line signal. Furthermore, the second
In the figure, the SCANNER START signal is a pulse-like signal, and when the circuit 30 receives this signal from 29, it starts searching for the radio line on which the idle line signal is being sent. On the other hand, it is supplied from circuit 39 to circuit 29.
The SCANNER STATE signal is a signal that informs that the wireless line through which the idle line signal is being sent has been established, and at this time the signal has a logic level of "1".

The effects of the present invention can be further enhanced by combining it with the following idle line signal detection method.
First, the idle line signal scanning circuit allocates the minimum time during which its detection system can detect the idle line signal as the idle line signal detection time for each channel, and the first idle line signal detection operation is performed for all channels. Then, from the second time onwards, the detection operation is performed only on the channel where the empty line signal was detected last time, and the channel for which the empty line signal is still detected after performing the detection operation a specified number of times is determined to be the empty line signal channel. If a line signal is not detected in any channel, it is determined that there is no line signal, and the line detection operation is repeated from the first time. If the idle line signal is detected in only one channel at the first time, the idle line signal component is detected only for the wireless line in question in the second time, and if the idle line signal level is detected again, the idle line signal component is detected for the wireless line in question. It is determined that a blank line signal is being sent.

As explained above, according to the present invention, since the detection operation is performed only on the channel where the idle signal was detected last time after the second time, the operation is performed reliably.
In particular, by closing the squelch circuit, the empty channel can be detected more quickly, and the effect is enormous.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a village telephone system to which the system according to the present invention is applied, and FIG. 2 is a block diagram of a vacant line signal scanning system according to the present invention. In the figure, 27d is a gate circuit for inhibiting the squelch circuit 27, and 30 is a blank line signal scanning circuit.

Claims (1)

[Claims] 1. When forming a mutual communication path between one master station and one of the many slave stations with which to communicate, one free channel among the multiple channels that is not currently being used for calls or data transmission is used. In a system in which a blank line signal is sent to a line channel and this blank line channel is used as a mutual signal path, the signal path provided in the signal path leading to the signal receiving circuit is closed during the blank line signal detection. Stopping the function and detecting the idle line signal for each channel with a minimum time during which the detection system of the idle line channel can detect the idle line signal, and the first time performing the idle line signal detection operation for all channels, From the second time onwards, signal detection is performed only on the channel where the empty line signal was detected last time, and after performing the detection operation a specified number of times, the channel on which the empty line signal is detected is determined to be the empty line channel, and the first time If the idle line signal is detected in only one channel, the second time the idle line signal component is detected only for the radio circuit concerned, and if the idle line signal level is detected again, the idle line signal is detected for the wireless circuit in question. A blank line signal scanning method characterized in that it is determined that a signal is being transmitted, and if a blank line signal is not detected in any channel, the first blank line detection is repeated.