Multiplex communications – Fault recovery
Reexamination Certificate
1999-03-15
2003-01-21
Ton, Dang (Department: 2732)
Multiplex communications
Fault recovery
Reexamination Certificate
active
06510134
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a non-break change-over device used for a redundancy system adapted to be multiplexed by using an active system and a standby system, which enables each of these two systems to be switched alternately, thus achieving an improvement of reliability.
2. Description of the Related Art
A redundancy system has been conventionally adopted in such transmission equipment and the like as require high reliability, which is designed to multiplex each of functional blocks, circuit boards or transmission paths constituting the transmission equipment by utilizing an active system and a standby system. In such a system, for example, a monitoring section loaded with firmware has been used to monitor each of multiplexed components of the device.
When a necessity occurs for, for instance, maintenance and checking in one information transmission system functioning as an active system, a switching signal providing instructions for switching from the standby state to an active state is fed from the monitoring section to the other information transmission system functioning as a standby system. When the standby system receives, from the firmware, an instruction for switching, an external switching signal is sent to the active system and thus switching between standby and active systems can be achieved through this mutual signal communications with a matched timing.
If a standby system receives, from the firmware, an instruction for switching, it sends out a switching request signal to an active system and, at the same time, it internally generates a switching signal and performs switching control therein. Because both frame pulses each controlling the active and standby system respectively have the same period, if these frame pulses are in phase with each other, switching between the active and standby systems can be achieved at a stroke within the same frame. However, due to a time-delay caused by a difference in the transmission paths extending from the same generating source, and to other conditions, these frame pulses for each system are not always in phase with each other. Accordingly, in the case where the frame of the active system leads slightly that of the standby system, if input timing of a switching instruction from the firmware is not matched, a switching of the standby system to an active state within the frame during which switching of the active system to a standby state has been performed cannot be achieved, causing any system not to function as an active one, i.e., possibly no operations of any system in some cases.
FIG. 8
shows a conventional redundancy system having first and second information transmission systems and a conventional non-break change-over device provided in relation thereto. The first and second information transmission systems,
1
and
1
′ are, for example, information processing devices which deal with information in units of frames defined by frame pulses having the same period and both of them have the equivalent functions. The conventional non-break change-over device
2
is provided which constitutes the redundancy system together with both information transmission systems
1
and
1
′.
The non-break change-over device
2
is provided with a monitoring section comprising firmware into which a monitoring program is stored. Also, the non-break change-over device
2
is provided with control sections
4
and
4
′, first D flip-flops
5
and
5
′ and second D flip-flops
6
and
6
′ corresponding to the information transmission systems
1
and
1
′ respectively.
Both of these information transmission systems
1
and
1
′ are equipped with control circuits
1
a
and
1
a
′ which are in advance set so that one information transmission system functions as a standby system and the other as an active system.
The monitoring section
3
is used to monitor the operational states of both the information transmission systems
1
and
1
′ and to send out a switching instruction signal
7
to either of control sections
4
or
4
′ corresponding to either of the information transmission systems
1
or
1
′ which is then functioning as a standby system when switching between the active and standby systems is required, including a case where malfunctions have occurred which are so slight as not to cause a stop page of transmission operations of currently operating information transmission systems
1
or
1
′, or a case where a necessity for maintenance and checking occurs in currently operating information transmission systems
1
or
1
′.
For example, while one information transmission system
1
is functioning as a standby system, if the control section
4
corresponding to this information transmission system
1
receives a switching instruction signal
7
, it feeds a switching request signal
8
to the control section
4
′ corresponding to the other information transmission system
1
′ and at the same time transfers a switching instruction signal
7
to the first flip-flop
5
corresponding to said information transmission
1
.
The first flip-flop
5
to which the switching instruction signal
7
is transferred from the control section
4
, when it receives a frame pulse
9
from the corresponding information transmission system
1
, feeds an output signal
10
, based on the transferred switching instruction signal
7
, to the second flip-flop
6
. When the second flip-flop
6
receives a switching timing pulse
12
from a switching timing pulse generating section
11
, it outputs an internal switching signal
13
, based on the output signal
10
sent from the first flip-flop
5
.
The internal switching signal
13
from the second flip-flop
6
is outputted as a switching signal for switching to an active state to the control circuit
1
a
of the information transmission system
1
functioning as a standby system, by which switching of the information system
1
from its standby state to an active state is achieved accordingly.
On the other hand, the currently operating control section
4
′, when it receives a switching request signal
8
from the control section
4
of said one information transmission system
1
, outputs a switching request signal
8
′ and a switching instruction signal
7
′. The standby control section
4
receiving the switching request signal
8
′ from the control section
4
′, because it has received said switching instruction signal
7
from the monitoring section, does not respond to the switching request signal
8
′ and ignores it. Also, when the first flip-flop
5
′ receiving the switching instruction signal
7
′ from the control section
4
′ is given a frame pulse
9
′ from the corresponding information transmission system
1
′, it outputs an output signal
10
′ to the second flip-flop
6
′ based on the switching instruction signal
7
′ as in the case of the first flip-flop
5
of the standby system.
The second flip-flop
6
′, when it receives a switching timing pulse
12
′ from a switching timing pulse generating section
11
′, outputs an internal switching signal
13
′ based on the output signal
10
′ from the first flip-flop
5
′.
The internal switching signal
13
′ from the second flip-flop
6
′ is fed as a switching signal for switching to a standby state to said control circuit
1
a
′ of the information transmission system
1
′ functioning as an active system, by which switching of the information transmission system
1
′ from its active state to a standby state is achieved accordingly.
Each of the switching timing pulse generating section
11
and
11
′ provided corresponding to each of the information transmission system
1
and
1
′ produces switching timing pulses
12
and
12
′ respectively, based on the frame pulses from each of the information transmission systems
1
and
1
′. Each o
Ezawa Takashi
Kitakoshi Manabu
Oki Electric Industry Co. Ltd.
Rabin & Berdo P.C.
Ton Dang
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