JPH0429088A - System and device for time supplementary - Google Patents

Abstract

PURPOSE:To automatically correct displayed time with high precision by constituting the time supplementary device generating a digital signal at reference time to be accessed freely from a subscriber terminal connected to a digital public communication network. CONSTITUTION:A digital public communication network 1 is connected to a time supplementary device 2, and the device 2 generates the digital signal displaying the reference time at the reference time. In the communication network 1, many subscriber terminals 3 are connected through a subscriber transmission path 4. In the terminal 3, a self-advancing digital clock circuit 5 is provided to display time by a clock signal generating itself, and a time correction circuit 6 is provided to correct the time of the digital clock circuit automatically by the digital signal received from the device 2 through the communication network 1. Thus, when receiving the digital signal displaying the reference time, the time of the digital clock circuit is automatically exchanged to the reception signal of the digital signal, and the self-advancing digital clock is corrected to the reference time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a system for transmitting time to a subscriber terminal device through a public communication network.

[Conventional technology]

Conventionally, in the telephone network, a time information device that continuously transmits the current time by voice and time signal is connected, and this is accessed by the subscriber's dial and the sound is transmitted as a time signal service called ``rl17''. Information can be obtained through signals.

There is also a method of broadcasting highly accurate time information as standard radio waves.

Furthermore, a highly accurate clock is installed as a master clock,
A method has long been known in which a pulse signal transmitted from a master clock is distributed to a slave clock, and the slave clocks operate in synchronization with the pulse signal.

[Problem to be solved by the invention]

In the above-mentioned telephone network time signal service, the time information is outputted by voice), and therefore it is not suitable for a device that automatically adjusts the displayed time of a clock using this time signal service.

Automatically correcting the displayed time requires a voice recognition device, which is extremely expensive.

Standard radio waves are widely used as a highly accurate time standard, but because they are broadcast using short waves, the radio wave propagation conditions become unstable depending on the region or inside buildings, and currently known devices will eventually become unstable. This is also an expensive device and requires a large antenna, making it unsuitable for general use. Furthermore, in order to use it as highly accurate time information, it is necessary to correct the propagation time of standard radio waves from the transmitting station to the receiving position, and this correction generally requires manual work.

The present invention focuses on the fact that with the spread of digital public communication networks, and that many digital terminal devices are equipped with a digital clock circuit, the present invention is inexpensive and has a simple configuration, and is stable and highly accurate. An object of the present invention is to provide a time supply method suitable for automatically correcting the display time of a digital clock circuit.

[Means to solve the problem]

The first point of the present invention is the time supply system. That is, a time supply device that generates a digital signal indicating a standard time at the standard time is connected to a digital public communication network. This time supply device is configured so that it can be freely accessed by a subscriber terminal connected to a digital public communication network via an exchange connection.

Alternatively, the time supply device is configured to periodically connect to the subscriber terminal by activation from the time supply device side. This subscriber terminal includes a digital clock circuit that displays the time using a clock signal generated by itself, and a time correction circuit that adjusts the time of the digital clock circuit using a digital signal received from the time supply device via a digital public communication network. circuit.

Further, the time adjustment circuit includes means for immediately returning the received digital signal to the time supply device via the digital public communication network, and the time supply device generates a digital signal indicating standard time. a means for measuring the time from when the returned digital signal is received from the digital public communication network; and a digital signal representing the measurement result of the means to be transmitted to the digital public communication network as delay time information within the line. The time adjustment circuit may further include means for re-adjusting the time of the digital clock circuit based on the received delay time information.

The second aspect of the present invention is a subscriber terminal device. That is, in a subscriber terminal device that is equipped with an interface that connects to a digital public communication network and a digital clock circuit that displays the time using a clock signal that it generates, a digital signal that displays the standard time that is received via the interface. The present invention is characterized by comprising a time adjustment circuit that automatically adjusts the time of a built-in digital clock circuit.

Furthermore, the subscriber terminal device of the present invention correctly corrects its own clock circuit to the standard time based on the time information received from the digital public communication network, and uses the clock circuit as a master clock to drive a plurality of slave clocks based on the standard time. It can be configured to do this.

[Effect]

In the system of the present invention, at least one time supply device is connected to a digital public communication network. This time supply device has clock information that displays standard time, displays the standard time on a digital signal, and transmits the digital signal to the digital public communication network at the displayed time. This time supply device is accessed from a subscriber terminal connected to the digital public communication network, and the subscriber terminal can receive a digital signal indicating standard time through the network.

The subscriber terminal has a built-in self-running digital clock. When a digital signal indicating the standard time is received, the self-running digital clock is corrected to the standard time by automatically replacing the time display of the digital clock with the reception signal of the digital signal. By displaying standard time in units of 1 second, 0.1 seconds, or 0.01 seconds, the precision of the digital clock on the subscriber terminal can be adjusted to an accuracy sufficient for various purposes. .

If the transmission time between the time supply device and the subscriber terminal in the digital public communication network becomes a problem due to the accuracy of the digital clock circuit installed in the subscriber terminal device, the present invention provides the following display. The time can be readjusted with even greater accuracy. That is, a digital signal indicating standard time is transmitted from the time supply device to the downlink, and the subscriber terminal that receives this transmits the digital signal back to the uplink immediately. The time supply device measures the time from transmitting a digital signal to the downlink until receiving the return signal. The measurement result is the time it takes for the signal to travel back and forth from the time supply device to the subscriber terminal, so calculate 1/2 of the measurement result, subtract it from the standard time display, and calculate the corrected time. Sends information to subscriber terminals. At the subscriber terminal, the displayed time is readjusted by replacing the corrected time information with the display of the built-in digital clock circuit. The display time re-corrected in this manner has extremely high accuracy, taking into account the transmission delay time of the digital public communication network.

In the device of the present invention, the time supply device is a fairly sophisticated device, but this device is installed by a person who operates a digital public communication network. A small number of devices are installed in one communication network depending on the traffic used. Access via the digital public network may be charged.

In contrast, general subscriber terminal devices have extremely simple configurations, and can be adapted to the built-in digital clock circuit in many subscriber terminal devices by adding a small amount of electronic circuitry.

If the subscriber terminal device is, for example, one standard clock device, the digital clock circuit of the subscriber terminal device can be used as a master clock, and the slave clocks can be driven from the master clock to allocate the time display. .

According to the present invention, each subscriber terminal within one digital public communication network can have one time, which is convenient from the viewpoint of communication network management.

Embodiment] FIG. 1 is a block diagram of an embodiment of the present invention. The digital public communication network 1 is, for example, an I5DN communication network. A time supply device 2 is connected to this public communication network 1. This time supply device 2 generates a digital signal indicating a standard time at the standard time.

A large number of subscriber terminals 3 are connected to this digital public communication network via subscriber transmission lines 4. FIG. 1 shows only one of a number of subscriber terminals. This subscriber terminal 3 includes a self-running digital clock circuit 5 that displays the time using a clock signal generated by itself, and a self-running digital clock circuit 5 that displays the time using a clock signal generated by itself, and a self-running digital clock circuit 5 that displays the time using a clock signal generated by itself, and a self-running digital clock circuit 5 that displays the time using a self-generated clock signal. and a time adjustment circuit 6 that automatically adjusts the time.

This time adjustment circuit 6 includes means for immediately returning the received digital signal to the time supply device 2 via the digital public communication network 1, and the time supply device 2 generates a digital signal indicating standard time. means for measuring the time from when the returned digital signal is received from the digital public communication network 1, and a digital signal representing the measurement result of this means as delay time information within the line to the digital public communication network l. Further, the time adjustment circuit 6 includes means for re-adjusting the time of the digital clock circuit 5 based on the received delay time information. The time supply device 2 includes a program processing circuit, a means for generating a digital signal indicating a standard time, and a means for transmitting the standard time to a digital public communication network and receiving the returned digital signal from the digital public communication network. The means for measuring the time until the end of the line and the means for transmitting a digital signal for re-correction based on the measurement result to the digital public communication network as delay time information within the line are realized by the program processing circuit.

The subscriber terminal device of the present invention includes an interface 30 for connection to a digital public communications network. The clock signal generated by the clock signal generation circuit 52 is counted by the counter 51 and used as the display time. This counter 51
The contents of are given to and displayed on the display 53, and also given as a time display of a child clock connected by wire or wirelessly from the distribution circuit 54. The time information is identified by the time information identification circuit 33 and given to the clock circuit 5 as a correction or re-adjustment signal. To adjust or re-adjust the time,
This is done by replacing the contents of this counter 51 with the received information.

FIG. 3 is a diagram showing a communication control procedure between the time supply device 2 and the subscriber terminal device 3 according to the embodiment of the present invention. In this example, a call is made from the subscriber terminal, and when the subscriber terminal dials the connection number of the time supply device and makes the call, and an exchange connection is established, the time supply device sends a response signal. ,
Next, a digital signal indicating the standard time is transmitted.

The subscriber terminal that receives this digital signal corrects the time by replacing the displayed time of the built-in clock circuit with the digital signal.

Simultaneously received digital signals are immediately sent back to the uplink.

On the other hand, the time supply device measures the time T from when a digital signal is transmitted on the downlink until the return signal of the digital signal arrives on the uplink, and calculates (1/2)T from the measurement result. The value obtained by subtracting this value from the standard time is displayed as a digital signal and transmitted to the subscriber terminal as a re-corrected digital signal. By replacing this re-corrected digital signal with the displayed time, the subscriber terminal can utilize highly accurate time information in which delays due to signal transmission time from the time supply device to the subscriber terminal have been corrected.

FIG. 4 is a block diagram of one embodiment of the present invention. A configuration is shown in which a signal indicating standard time is distributed from a digital public communication network 1 to a subscriber terminal 3.

A time supply device 2, which is a time supply source, is connected to the digital public communication network 1. A subscriber terminal station 11 is arranged in the digital public communication network 1, and a clock circuit 5 is provided in the subscriber terminal 3.

The signal representing the standard time generated from the time supply device 2 is
The time information is provided to the subscriber terminal 3 via the subscriber terminal equipment 11 and further via the subscriber transmission path 4, and the time information is identified as described above and provided to the clock circuit 5. The displayed time of this clock circuit 5 is distributed to each slave clock 55 via a time distribution circuit 54 by wire or wirelessly.

FIG. 5 is a diagram showing the state of information strings on the subscriber transmission line 4. As shown in FIG. A digital signal indicating the standard time is transmitted to the subscriber transmission line 4 together with a general information string. The information string is 1
There are two areas in the frame: control overhead and information, and time information can be placed in either of these areas, but in this case, time information is placed in the information area, and a bit for transmission delay measurement is also set. Give an example. The signals in the upper row of FIG. 5 indicate the outward route (signals from the time supply device to the subscriber terminal), and the signals in the lower row indicate the return route (signals from the subscriber terminal to the time supply device).

The time supply device measures the above-mentioned time T using the transmission delay measurement bit. In general, the outbound delay and the return delay are approximately equal, and the turnaround delay within the subscriber terminal can be ignored, so a value obtained by halving this time T can be used as the correction value. The time supply device makes this correction and transmits a value obtained by subtracting this correction value from the standard time (advancing the time). This modification can also be configured to be performed on the subscriber terminal side by transmitting information to the subscriber terminal.

Modification of the delay time required for transmission can also be applied between the master and slave clocks within the subscriber terminal.

〔Effect of the invention〕

As described above, according to the present invention, standard time information can be appropriately used at subscriber terminals connected to a digital public communication network. The configuration of the present invention is particularly advantageous in that the device configuration on the subscriber terminal side is simple and highly accurate time information can be used at low cost.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention. FIG. 2 is a configuration diagram of a subscriber terminal according to an embodiment of the present invention. FIG. 3 is a diagram showing a communication control procedure. FIG. 4 is a configuration diagram of an embodiment of the present invention. FIG. 5 is a diagram illustrating signals in an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1...Digital public communication network, 2...Time supply device, 3...Subscriber terminal, 4...Subscriber transmission line, 5...
・Clock circuit, 6...Modified circuit Patent applicant Nippon Telegraph and Telephone Corporation Representative Patent attorney Nao Takashi Ide Diagram Control procedure Diagram 3 Diagram

Claims (1)

[Claims] 1. A time supply device connected to a digital public communication network and generating a digital signal indicating a standard time at the standard time; and a subscriber terminal connected to the digital public communication network. , the subscriber terminal includes a digital clock circuit that displays the time using a self-generated clock signal, and a digital clock circuit that automatically displays the time of the digital clock circuit using a digital signal received from the time supply device via the digital public communication network. and a time adjustment circuit that adjusts the time. 2. The time adjustment circuit includes means for immediately returning the received digital signal to the time supply device via the digital public communication network, and the time supply device includes:
means for measuring the time from when a digital signal indicating standard time is generated until the returned digital signal is received from the digital public communication network; 2. The time according to claim 1, further comprising means for transmitting delay time information to a digital public communication network, and further comprising means for re-adjusting the time of said digital clock circuit based on said received delay time information. Supply method. 3. In a subscriber terminal device equipped with an interface for connection to a digital public communication network and a digital clock circuit that displays the time using a self-generated clock signal,
A subscriber terminal device comprising a time adjustment circuit that automatically adjusts the time of the digital clock circuit based on a digital signal indicating the standard time received via the interface. 4. The subscriber terminal device according to claim 3, wherein the digital clock circuit is a master clock, and further comprises means for distributing the time display of the master clock to a plurality of slave clocks via a wired line or a wireless line. subscriber terminal equipment.