JP3424121B2 - Digital network synchronization method and digital key telephone system using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention eliminates the existing network clock transmission line, which is required mainly for exclusively transmitting the network clock generated on the basis of the clock extracted from the digital network. A digital network synchronization method for establishing network synchronization of an entire system based on a network clock generated by using an empty time slot of a digital data signal transmitted to a data transmission line (normally called PCM highway), and The present invention relates to a small-sized digital button telephone system to which it is applied.

[0002]

2. Description of the Related Art Conventionally, in this kind of digital network synchronizing method, in a digital button telephone system which is connected to an ISDN digital network by application of ISDN or the like, for example, the D units are connected and arranged as interface units.
There is one DPLL mounting unit including a PLL and a plurality of network synchronization units, and one master unit that extracts a clock from a digital network in each network synchronization unit and generates a network clock that is a master network clock is a network. The clock is sent to the network clock transmission line as a network clock signal, and the DPLL mounting unit receives the network clock signal from the network clock transmission line and generates a system clock signal synchronized based on the network clock to generate a system clock. The data is sent to the transmission line, and thereby the entire system is synchronized with the DPLL mounting unit and the plurality of network synchronization units connected to the system clock transmission line.

FIG. 3 is a block diagram showing the basic configuration of a conventional digital button telephone system to which such a digital network synchronization method is applied.

This digital key telephone system is a DP
One DPLL mounting unit 10 'including the LL 10a'
And a plurality of network synchronization units 30 ₁ to 30 _n are connected to each other as interface units so as to be clock-synchronized with the digital network DN via the network synchronization unit 30 ₁ , and the DPLL mounting unit 1 is also provided.
0'and each of the network synchronization units 30 ₁ to 30 _n , digital data which is a transmission path of a digital data signal for exchanging digital data such as time-division multiplexed voice transmitted from the digital network DN. DPLL based on the clock transmitted from the transmission line S2, the digital network DN
The system clock transmission line S1 for transmitting the system clock signal generated by the mounting unit 10 'in synchronization is connected in common, and the DPLL mounting unit 10' and one of the network synchronization units 30 ₁ to 30 _n are connected. A dedicated network clock transmission line S3 for establishing network synchronization of the entire system is connected to one master unit.

Namely, in this digital key telephone system, the network synchronization unit 30 _one of the plurality of network synchronization unit 30 ₁ to 30 _n has a master unit, and extracts the master network clock from the digital network DN network A system clock signal that is sent as a clock signal to the network clock transmission line S3, and the network clock signal from this network clock transmission line S3 is received by the DPLL 10a 'of the DPLL mounting unit 10' and synchronized based on the network clock signal. Of the DPLL mounting unit 10 connected to the system clock transmission line S1 as a result of transmitting the system clock signal to each of the network synchronization units 30 ₁ to 30 _n by generating and transmitting to the system clock transmission line S1. cis based on the system clock signal by 'and the network synchronization unit 30 ₁ to 30 _n Network synchronization of the entire arm is adapted to be taken.

[0006]

In the case of the digital button telephone system described above, a system clock transmission line, a digital data transmission line, and a network clock are provided for the DPLL mounting unit and the master unit among the network synchronization units. In addition to connecting each of the transmission lines and connecting the digital data transmission line to the PLL mounting unit and all the network synchronization units, a master network clock extracted from the digital network by the master unit is used as a network clock signal. It is sent to the clock transmission line, and the DPLL of the DPLL mounting unit generates a system clock signal that is synchronized based on the network clock signal from the network clock transmission line and outputs it to the system clock transmission line. As a result of the system clock signal being transmitted to the unit, the system The network synchronization of the entire system is taken. With such a configuration, a dedicated dedicated network synchronization system for the DPLL mounting unit and the master unit of each network synchronization unit is provided. Since it is necessary to connect the network clock transmission line, the wiring connection of the entire system is complicated, and the increase in size cannot be avoided.
Although there is a vacant time slot in the digital data signal transmitted / received by the digital data transmission line connected to the PLL mounting unit and each network synchronization unit as a CM highway, this part is not effectively utilized, which is rational. However, there is a problem that the network synchronization of the entire system cannot be achieved.

The present invention has been made to solve such a problem, and its technical problem is to eliminate a network clock transmission line and to digitally network the network so that the network can be reasonably synchronized with the entire system. It is to provide a synchronization method and a digital button telephone system to which the synchronization method is applied and which can be configured in a small scale and simply.

[0008]

According to the present invention, one DPLL mounting unit and a plurality of network synchronization units are connected to each other as interface units so as to be clock-synchronized with a digital network, and digital buttons are provided. Digital data for exchanging time-division multiplexed digital data transmitted from the digital network commonly connected to the DPLL mounting unit and the plurality of network synchronization units in a telephone system A digital data transmission line that is a signal transmission line and a system clock transmission line that is a system clock signal transmission line that synchronizes the entire system based on the clock transmitted from the digital network When performing the digital network synchronization, the clock is supplied from the digital network of the plurality of network synchronization units. A master unit that outputs a network clock signal to serve as a master network clock generates the network clock signal by using an empty time slot of the digital data signal transmitted to the digital data transmission line and outputs the digital clock signal. The data is transmitted to the data transmission line, and the DPLL mounting unit receives the network clock signal from the digital data transmission line and synchronizes the system clock signal to generate the system clock signal and transmits the system clock signal to the system clock transmission line. And the DPL connected to the system clock transmission line.
By the L mounting unit and the plurality of network synchronization units, a digital network synchronization method for obtaining network synchronization of the entire system based on the system clock signal can be obtained.

Further, according to the present invention, one DPLL mounting unit and a plurality of network synchronization units are connected and arranged as interface units so as to be clock-synchronized with a digital network, and the DPLL mounting unit is mounted. A digital data transmission line which is a transmission path of a digital data signal for enabling time-division multiplexed digital data transmitted from the digital network to the unit and the plurality of network synchronization units, and the digital network In a digital button telephone system in which a system clock transmission line that is a system clock signal transmission line that is network-synchronized for the entire system based on the clock transmitted from , Which is included in the digital data transmitted from the digital network to the digital data transmission line. A master clock that extracts a clock to generate a network clock signal as a master network clock and sends the generated network clock signal to the digital data transmission line. The DPLL mounting unit receives the network clock signal from the digital data transmission line. Then, the system clock signal is generated by synchronizing and then sent to the system clock transmission line, and D
With the PLL mounting unit and the plurality of network synchronization units, a digital key telephone system can be obtained in which network synchronization of the entire system is performed based on the system clock signal sent to the system clock transmission line.

Further, according to the present invention, in the digital key telephone system, the DPLL mounting unit preliminarily designates an empty time slot for the master unit, and the master unit transmits to the digital data transmission line. A frame synchronization signal indicating the start of an empty time slot in the digital data signal is extracted to generate an empty time slot mask signal corresponding to the position of the empty time slot, and the empty time slot mask signal and the digital network are extracted. The network clock signal is sent to the digital data transmission line by adding a logical product signal obtained by ANDing with the network clock to the digital data signal of the designated empty time slot, and the DPLL of the DPLL mounting unit is sent. Then, the network clock signal by AND signal Is sampled at a predetermined position of the rectangular wave indicated by the reference sampling signal, and the period of the frame synchronization signal is adjusted so that the rising position of the rectangular wave of the network clock signal matches the predetermined position. A digital button telephone system is provided that generates a clock signal.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A digital network synchronization method of the present invention and a digital key telephone system to which the method is applied will be described in detail below with reference to the drawings.

First, the outline of the digital network synchronization method of the present invention will be briefly described. According to this digital network synchronization method, one DPLL mounting unit and a plurality of network synchronization units are connected to each other as interface units so as to be clock-synchronized with a digital network to form a digital button telephone system. A digital data transmission line which is a transmission path of a digital data signal for making it possible to exchange time division multiplexed digital data transmitted from a digital network commonly connected to the unit and each network synchronization unit. When performing digital network synchronization using the system clock transmission line that is the system clock signal transmission line that synchronizes the entire system based on the clock transmitted from the digital network, among the network synchronization units Network clock that becomes the master network clock by extracting the clock from the digital network One master unit for transmitting a signal generates a network clock signal by using an empty time slot of the digital data signal transmitted to the digital data transmission line and transmits it to the digital data transmission line. A system clock signal is generated by receiving and synchronizing the network clock signal from the data transmission line, and is sent to the system clock transmission line, and the DPLL mounting unit connected to the system clock transmission line and each network synchronization. The unit synchronizes the network of the entire system based on the system clock signal.

According to such a digital network synchronization method,
In the conventional digital network synchronization method, the dedicated network clock transmission line required for network synchronization of the entire system is eliminated, and the master unit of each network synchronization unit is transmitted to the digital data transmission line. A digital clock signal indicating a master network clock generated by itself using an empty time slot of the digital data signal is sent to the digital data transmission line, and the DPLL mounting unit generates a system clock signal synchronized with the network clock signal. Since it suffices to have the function of sending to the system clock transmission line,
With a small scale configuration, network synchronization of the entire system can be reasonably achieved.

FIG. 1 is a block diagram showing the basic configuration of a digital key telephone system according to an embodiment to which the digital network synchronizing method of the present invention is applied.

This digital button telephone system has a DP
One DPLL mounting unit 10 including the LL 10a and a plurality of network synchronization units 20 _{1 to} 20 _n are connected and arranged as interface units so as to be clock-synchronized with the digital network DN via the network synchronization unit 20 _1. digital network D relative with, DPLL mounting unit 10 and the network synchronization unit 20 ₁ to 20 _n comprising Te
Digital data transmission line S2, which is a transmission path of a digital data signal for enabling time-division multiplexed digital data such as voice data transmitted from N to be exchanged, and a digital network D
A system clock transmission line S1 for transmitting a system clock signal generated by the DPLL mounting unit 10 in synchronization based on the clock transmitted from N is connected in common, and each network synchronization unit 20 is connected. ₁ ~
20 _n is a digital data transmission line S from the digital network DN.
2 includes a master unit (network synchronization unit 20 ₁ ) for extracting a clock included in the digital data transmitted to 2 to generate a network clock signal as a master network clock and sending it to the digital data transmission line S2. Cage, DP
The LL mounting unit 10 receives the network clock signal from the digital data transmission line S2 and synchronizes it to generate a system clock signal, which is then sent to the system clock transmission line S1, and the DPLL mounting unit and each network synchronization. The units 20 _{1 to} 20 _n are system clock transmission lines S1
The network synchronization of the entire system is established based on the system clock signal sent to.

Of these, the DPLL mounting unit 10 is
As will be described later, the master unit (network synchronization unit 2
0 ₁ ), an empty time slot is designated in advance, and the master unit (network synchronization unit 20 ₁ )
A frame synchronization signal indicating the start of an empty time slot in the digital data signal transmitted to the digital data transmission line S2 is extracted to generate an empty time slot mask signal according to the position of the empty time slot, and the empty time slot is also generated. Mask signal and digital network D
A network clock signal is sent to the digital data transmission line S2 by adding a logical product signal obtained by ANDing with the network clock extracted from N to the digital data signal of the designated empty time slot, and the DPLL In the DPLL 10a of the mounting unit 10, the network clock signal based on the logical product signal is sampled at a predetermined position of the rectangular wave indicated by the reference sampling signal so that the rising position of the rectangular wave of the network clock signal matches the predetermined position. Then, the system clock signal to be sent to the system clock transmission line S1 is generated after adjusting the cycle of the frame synchronization signal.

[0017] That is, in this digital key telephone system, a plurality of network synchronization unit 20 ₁ to 20 with the network synchronization unit 20 ₁ of _n is in the master unit, which has heretofore been required network clock transmission line S3 Is excluded, and the network clock signal indicating the master network clock is generated by using the empty time slot of the digital data signal transmitted to the digital data transmission line S2 in the network synchronization unit 20 ₁ to generate the digital data transmission line. Send to S2,
By receiving the network clock signal from the digital data transmission line S2, the DPLL 10a of the DPLL mounting unit 10 generates a synchronized system clock signal based on the network clock signal and outputs it to the system clock transmission line S1. As a result of the system clock signal being transmitted to each network synchronization unit 20 _{1 to} 20 _n , the DPLL mounting unit 10 and each network synchronization unit 20 _{1 to} 20 _n connected to the system clock transmission line S1 are based on the system clock signal. The entire system is synchronized with the network.

FIG. 2 shows a master unit (network synchronization unit 20 ₁ ) provided in this digital key telephone system.
3 is a timing chart exemplifying a signal operation process between the and the DPLL mounting unit 10.

Here, the DPLL mounting unit 10 is previously prepared.
Specifies a free time slot included in the digital data signal to the network synchronization unit 20 ₁ via the digital data transmission line S2, and the network synchronization unit 20 ₁ transmits the digital data signal to the digital data transmission line S2 according to the designation. Of the empty time slot is extracted to generate the empty time slot mask signal b corresponding to the position of the empty time slot, and the empty time slot mask signal b and the network extracted from the digital network DN. AND with the clock (AN
The network clock signal is sent to the digital data transmission line S2 by adding the logical product signal obtained in step D) to the digital data signal in the designated empty time slot.

Therefore, the DP of the DPLL mounting unit 10
In the LL 10a, the network clock signal by the logical product signal transmitted through the digital data transmission line S2 is sampled at a predetermined position C indicating the rising edge of the rectangular wave shown in the reference sampling signal e, and for example, the network clock signal c Since the rectangular wave sampling data is in the state of 1, the period of the frame synchronization signal a is adjusted so that the rising portion of the rectangular wave is moved rightward as indicated by the arrow A. Is 0, the period of the frame synchronization signal a is adjusted so that the rising portion of the rectangular wave is moved leftward as indicated by the arrow B, and as a result, the predetermined position C of the rectangular wave indicated by the reference sampling signal e is adjusted. The frame synchronization signal a so that the rising edges of the rectangular wave of the network clock signal transmitted by
Of the network synchronization units 20 _{1 to} 20 _n by generating a system clock signal and transmitting the system clock signal to the system clock transmission line S1 after adjusting the period.
To the network synchronization of the entire system.

That is, in the case of this digital key telephone system, as compared with the conventional system shown in FIG. 3, since the network clock transmission line S3 is eliminated, the wiring connection is simplified and the structure is reduced in scale. is in and, moreover to obtain a logical product signal without using a network clock that the network synchronization unit 20 ₁ is directly extracted from the digital network DN in network clock transmission line S3 as in the prior art is the master unit as a master network clock A system in which a network clock signal indicating a master network clock indirectly used for inputting one of the two is sent to the digital data transmission line S2, and the DPLL 10a of the DPLL mounting unit 10 is synchronized based on the network clock signal. The system clock transmission is performed by the configuration in which the clock signal is generated and sent to the system clock transmission line S1. It has become reasonably possible configure network synchronization of the entire system according to the connected DPLL mounting unit 10 and the network synchronization unit 20 ₁ to 20 _n to the line S1.

[0022]

As described above, according to the digital network synchronization method of the present invention, one master unit among a plurality of network synchronization units connected and arranged as an interface unit mutually functions as a digital data transmission line. The idle time slot of the transmitted digital data signal is used to generate a network clock signal indicating the master network clock and send it out to the digital data transmission line, and the DPLL mounting unit converts it into a network clock signal from the digital data transmission line. An entire system based on the system clock signal by the DPLL mounting unit and a plurality of network synchronization units connected to the system clock transmission line by generating a system clock signal synchronized based on the system clock transmission line Since I am trying to synchronize the network of
In the past, the dedicated network clock transmission line, which was required to establish network synchronization of the entire system, was eliminated, and the network clock of the system clock signal transmitted to the system clock transmission line was directly used as in the past. The network synchronization of the entire system can be reasonably achieved only by indirectly using it as a master network clock. In addition, in the digital key telephone system to which this digital network synchronization method is applied, the network clock transmission line is eliminated, so that the wiring connection can be simplified and the configuration can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing a basic configuration of a digital key telephone system according to an embodiment to which a digital network synchronization method of the present invention is applied.

FIG. 2 is a timing chart exemplifying signal operation processing between a master unit and a DPLL mounting unit of a network synchronization unit included in the digital button telephone system shown in FIG.

FIG. 3 is a block diagram showing a basic configuration of a digital key telephone system to which a conventional digital network synchronization method is applied.

[Explanation of symbols]

10, 10 'DPLL implementation units _{10a, 10a' DPLL 20 1 ~20} n, 30 1 ~30 n network synchronization units S1 system clock for transmitting line S2 digital data transmission line S3 network clock for transmitting line DN Digital Network

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H04Q 11/04 304 H04L 7/033 H04M 1/723 H04M 3/00 H04Q 3/58 107

Claims (3)

(57) [Claims] 1. One DPLL (Dgital Pha)
se Lock Loop) mounting unit and a plurality of network synchronizing units are connected and arranged as interface units so as to be clock-synchronized with a digital network to form a digital button telephone system, and the DPLL mounting unit and the plurality of DPLL mounting units. A digital data transmission line which is a transmission path of a digital data signal for enabling time-division multiplexed digital data transmitted from the digital network commonly connected to the network synchronization unit and the digital When performing digital network synchronization using a system clock transmission line that is a system clock signal transmission line in which network synchronization of the entire system is performed based on a clock transmitted from the network, the plurality of network synchronization units A network clock that becomes the master network clock by extracting the clock from the digital network. One master unit for transmitting a clock signal generates the network clock signal by using an empty time slot of the digital data signal transmitted to the digital data transmission line and transmits it to the digital data transmission line. , The DPLL mounting unit receives and synchronizes the network clock signal from the digital data transmission line to generate the system clock signal, and sends the system clock signal to the system clock transmission line to transmit the system clock signal. A digital network synchronization method, characterized in that the DPLL mounting unit and a plurality of network synchronization units connected to a line establish network synchronization of the entire system based on the system clock signal. 2. One DPLL (Dgital Pha)
se lock loop) mounting unit and a plurality of network synchronization units are connected to each other as an interface unit so as to be clock-synchronized with a digital network, and the DPLL mounting unit and the plurality of network synchronization units are connected to each other. System based on a digital data transmission line which is a transmission path of a digital data signal for exchanging time division multiplexed digital data transmitted from the digital network and a clock transmitted from the digital network. In a digital button telephone system in which a system clock transmission line, which is a transmission line of a system clock signal synchronized with the network, is commonly connected, the plurality of network synchronization units transmit the digital data from the digital network. Clock included in the digital data transmitted to the utility line Extracted and generates a network clock signal serving as a master network clock comprises one master unit to be sent to the digital data transmission line, the DPLL
The mounting unit generates the system clock signal by receiving and synchronizing the network clock signal from the digital data transmission line, and then sends the system clock signal to the system clock transmission line. The digital key telephone system, wherein a plurality of network synchronization units establish network synchronization of the entire system based on the system clock signal sent to the system clock transmission line. 3. The digital key telephone system according to claim 2, wherein the DPLL mounting unit preliminarily designates the empty time slot for the master unit, and the master unit is for transmitting the digital data. A frame synchronization signal indicating the start of the empty time slot in the digital data signal transmitted to the line is extracted to generate an empty time slot mask signal according to the position of the empty time slot,
The digital data transmission by adding a logical product signal obtained by ANDing the empty time slot mask signal and the network clock extracted from the digital network to the digital data signal of the specified empty time slot. The network clock signal is transmitted to the utility line, and the D
In the DPLL of the PLL mounting unit, the network clock signal based on the logical product signal is sampled at a predetermined position of the rectangular wave indicated by the reference sampling signal so that the rising position of the rectangular wave of the network clock signal is at the predetermined position. A digital network synchronization system for generating the system clock signal after adjusting the period of the frame synchronization signal so as to be matched.