JPH02126792A - Automatic switching system for network synchronizing clock - Google Patents

Abstract

PURPOSE:To automatically switch a network synchronous clock at the time of line disconnection by connecting the plural network synchronous clocks in a bus format, and supplying any one of the network synchronous clock onto a bus. CONSTITUTION:A signal detecting means 204 checks whether or not a signal exists on a point B on a network synchronous clock supplying line. A signal detecting means 203 checks whether or not the signal exists on an A point output in a dividing circuit 202. When the signal exists on the point A, whether or not the signal exists on the point B is checked again. At such a time, when another digital trunk does not exist, it is judged that the signal does not exist on the point B, a switch 20 is turned on, and the network synchronizing clock is outputted to a network synchronizing clock supply line 6. When the digital line is disconnected, since the signals on the A and B points disappear, a switch 207 is turned off. Hereafter, other digital trunks 2 and 7 start to supply the network synchronous block in the same sequence. Thus, speaking can be continued even at the time of the line disconnection.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention is a digital electronic exchange (hereinafter referred to as DPBX).
The present invention relates to an automatic network synchronization clock switching system for automatically selecting network synchronization clocks from a plurality of digital lines and supplying them to a network synchronization circuit.

(Prior Art) When a DPBX is connected to a digital line, it is necessary to synchronize the internal clock of the DPI (X) with the clock of the digital line.

FIG. 3 is a block diagram showing the flow of clocks when a conventional r)PBX is connected to a digital line. In Fig. 3, 31 is a DPBX, 32 is a digital trunk connected to a digital line, and 33 is a network synchronization circuit (PI, L).
, :34 is a time division switch circuit, and 35 is an extension card connected to an extension telephone.

Next, the operation of the above conventional example will be explained. In FIG. 3, a network synchronization circuit (PLL) 33 generates a basic clock in the DPBX in synchronization with a network synchronization clock extracted by a digital trunk 32, and a time division switch circuit (NW) 34 generates a basic clock in the DPBX.
is supplied to. The time division switch circuit 34 supplies a PCM clock to the digital trunk 32 and the extension card 35 based on the basic clock supplied from the network synchronization circuit 33. In this way, all the clocks in the DPI3 reactor.

(Problem to be Solved by the Invention) However, in the above-mentioned conventional clock supply system, when accommodating a plurality of digital lines, only one network synchronized clock is required. You need to decide on the line. If the multiple digital lines are all NTT lines, the clocks of all the digital lines are synchronized, so you can use any one line, but if the digital line that is the source of the network synchronized clock goes down. Alternatively, in the case of a disconnection, there is a problem that network synchronization with other digital lines cannot be achieved.

The present invention solves these conventional problems,
The purpose of this system is to provide an excellent network synchronization clock automatic switching system that can automatically synchronize the network with any other digital line even if the digital line that is the source of network synchronization goes down or is disconnected. be.

(Means for Solving the Problems) In order to achieve the above object, the present invention connects a plurality of network synchronized clocks in a bus format, so that each bus is always supplied with one of the network synchronized clocks, and the network synchronization When the clock stops, it automatically switches to one of the other network synchronized clocks.

(Function) Therefore, according to the present invention, even if the digital line that is the source of network synchronization among the plurality of digital lines accommodated in the DPRX goes down or is disconnected, the other digital lines are automatically synchronized. By switching network synchronization to the clock,
You can continue talking to other digital lines without interruption.

(Embodiment) FIG. 1 shows the configuration of a network synchronized clock automatic switching circuit according to an embodiment of the present invention. In the first piil, 2
is a digital trunk, a digital line.

A line interface 201 connected to the PCM highway and the clock, a frequency divider circuit 202 that divides the clock extracted from the digital line signal by the line interface 201 to the same frequency as the network synchronized clock, and a frequency divider circuit 2.
Detection means 203 for detecting the output from 02, and signal detection means 2 for detecting the signal on the network synchronization clock supply line 6.
04 and 1 frequency divider circuit 202 and the phase of the signal on the network synchronized clock supply line 6.
5, and outputs from the signal detection means 203 and 204 and the phase comparison means 205 turn on and off the switch 207 to control whether or not the output from the divide-by-1 circuit 202 is output to the network synchronized clock supply line 6. It is composed of a control section 206 and a switch 207. 7 is another digital trunk having the same circuit configuration as digital trunk 2; FIG. 2 is a flowchart showing the operation of the embodiment shown in FIG.

Next, the operation of the above embodiment will be explained with reference to FIGS. 1 and 2. In FIG. 1, the output point of the divide-by-1 circuit 202 is set to A
Assuming that the point connected to the network synchronization clock supply line 6 is the point B, the control unit 206 first uses the signal detection means 204 to check whether there is a signal on the network synchronization clock supply line (point B). (Fig. 3 St). B immediately after power on
Since there is no signal at the point, the signal detecting means 203 checks whether there is a signal at the output of the frequency dividing circuit 202 (point A) (FIG. 2, S). If the digital trunk 2 is connected to a digital line, a signal should be output.

If there is a signal at point A, it is checked again whether there is a signal at point B (St in Fig. 2). At this time, if there is no other digital trunk or if the network synchronized clock has not yet been output to the network synchronized clock supply line 6, it is determined that there is no signal at point B, and the switch 207 is not turned on. ), outputs its own network synchronization clock to the network synchronization clock supply line 6, and returns to S□ in FIG. From now on, since there will be a signal output from point B, the i quantity detection means 203 will check whether there is a signal at point A (see Fig. 2).
2), since there is naturally a signal at point A at this time, the phase comparison means 205 compares the phases of the signals at point A and point B (S3 in FIG. 2). If the phases are the same, it is determined that they are the same signal (that is, the signal that they are outputting), and the switch 207 remains on (FIG. 2, 84).

If the digital line connected to the digital trunk 2 is disconnected, there will be no signal at point A or point B, so the switch 207 will be turned off (S, Fig. 2).
After this, other digital trunks will start providing network synchronized clocks in a similar sequence as described above. At this time, even if the disconnection of the digital line connected to digital trunk 2 is repaired, the
When the phases of point and point B are compared by the phase comparison means 205 (
Figure 2 SJ) Since the phases are not the same, switch 207
remains off (Fig. 2S,).

In this way, according to the above embodiment, even if the digital line that is the source of network synchronization among the plurality of digital lines accommodated in the DPBX goes down or is disconnected, the clocks of the other digital lines are automatically updated. By switching to network synchronization, calls can continue without interruption except for the digital line that is down.

(Effects of the Invention) As is clear from the above embodiments, the present invention provides automatic synchronization even if the digital line on which network synchronization is based among the plurality of digital lines accommodated in the DPBx goes down or is disconnected. By switching the network synchronization to the clock of another digital line, it has the effect that calls can be continued without interruption except for the digital line that is down.

[Brief explanation of drawings]

FIG. 1 is a network synchronized clock switching circuit located in a digital trunk in one embodiment of the present invention, and FIG. 2 is a flowchart showing the operation of the circuit of FIG. 1. FIG. 3 is a block diagram showing the flow of clocks when a conventional DPBX is connected to a digital line. 2.7.32...Digital trunk, 6...Network synchronization clock supply line, 31...Digital electronic exchange (DP RX), 33...Network synchronization circuit, 34...
Time division switch circuit (NW), 35... Extension card, 201... Line interface, 202... Frequency dividing circuit, 203.204... Signal detection means, 205...
- Phase comparison means, 206...control unit. 207...Switch. Patent applicant: Matsushita Electric Industrial Co., Ltd.

Claims (1)

[Claims] For the network synchronization clock supply line to the network synchronization circuit, which is required when a digital electronic exchange is connected to a digital line,
Network synchronized clock outputs of a plurality of digital trunks are connected in a bus form, and in each digital trunk, means for detecting a network synchronized clock from a digital line, means for detecting a signal on a network synchronized clock supply line, and a network means for comparing the phase of the signal on the synchronized clock supply line and the network synchronized clock from the digital line; if there is a signal on the network synchronized clock supply line, the network synchronized clock is not output; otherwise, the network synchronized clock is output; A network synchronized clock automatic switching system characterized by automatically switching between multiple network synchronized clocks by controlling the output to stop if the phases are not the same in the event of a collision.