Patent Application
20070064924
1. Field of the Invention
The present invention relates to digital communication systems, more particularly to the configuration of an interface device and a protection device in the digital communication system.
2. Description of the Prior Art
Conventional digital communication systems have developed to form various standards such as T1, T3, E1, E3, DS3 (Digital Signal 3), SDH9 (Synchronous Digital Hierarchy), SONET (Synchronous Optical NETwork), etc.
In the systems, communications are carried out through various interface devices, such as transmitters, receivers, transceivers, etc. In order to protect the communications from interruption by the failure of the interface devices, protection or backup devices with the same communication functions are typically adopted to replace the communications in the interface devices in time once the interface devices fail.
Typically, the interface devices and the protection devices are configured to form two protection modes, i.e. 1+1 and N+1 protection modes, where the 1+1 protection mode uses one protection device for one interface device, while the N+1 protection mode uses one protection device for N (more than one) interface devices.
An interface device 102 placed on a module (a board, or card) 101 and a protection device 104 placed on a module (a board, or card) 103 are configured with relay contacts 106, 107, 108 and 109 as well as a transformer 110. The primary winding of the transformer 110 is connected to the relay contacts 106 and 107, and the secondary winding of the transformer 110 is connected to other devices. The transformer 110 is for impedance match with other devices. Such relay contacts are properly controlled to make the interface device 102 through a port thereon communicate with other interface device(s) when the interface device 102 is in normal state, and make the protection device 104 replace the communication in the interface device 102 when the interface device 102 fails.
The relay devices for such communications are generally bulky. Thus, the relay contacts 106-109 and the transformer 110 are placed on a separate module (a board, or card) 105. And the relay devices require additional control signals and consume a large amount of power. The above disadvantages will be exacerbated when the number of the interface device in the system increases. Further, the relay contacts have slow switching times, which would result in the loss of data and even the loss of frame in the communications. Although the relay devices can be replaced by analog switches for better performances, such analog switches still occupy somewhat space and consume somewhat power.
An improvement has been developed, as shown in
With the interface device 202 and the protection device 204, the ports thereon for communication can be connected in parallel and then connected to the primary winding of a transformer 207 to obtain the same failure protection function but without the use of the relay devices or analog switches. Hence, the configuration of
However, for maintenance, the connection of the ports of the interface device 202 and the protection device 204 as well as the primary winding of the transformer 207 must be placed in a separate module (a board, or card) 205, and the transformer 207 is also placed in a separate module (a board, or card) 206. Such arrangement result in the complication and higher cost of the system.
Therefore, there is a need for a configuration of the interface device and the protection device in the digital communication system, which has a simplified arrangement and lower cost while without the disadvantages caused by the use of the relay devices or analog switches.
A general object of the present invention is to provide a configuration of an interface device and a protection device in a digital communication system, thereby making the system have a simplified arrangement and lower cost while without the disadvantages caused by the use of the relay devices or analog switches.
According to one aspect, the present invention provides a method of configuring an interface device and a protection device in a digital communication system, the interface device having a first port for communicating with other devices, the first port being in a high-impedance state when the interface device fails, the protection device having a second port for replacing the communication of the interface device when the interface device fails, the second port being in a high-impedance state when the protection device is not in the replacing state, the method comprising the steps of providing a first transformer having a primary winding and a secondary winding, the primary winding of the first transformer being in series configuration with the first port of the interface device; providing a second transformer having a primary winding and a secondary winding, the primary winding of the second transformer being in series configuration with the second port of the protection device; and connecting the secondary winding of the first transformer in parallel with the secondary winding of the second transformer.
According to another aspect, the present invention provides a digital communication system comprising an interface device and a protection device, the interface device having a first port for communicating with other devices, the first port being in a high-impedance state when the interface device fails, the protection device having a second port for replacing the communication of the interface device when the interface device fails, the second port being in a high-impedance state when the protection device is not in the replacing state, the system further comprising a first transformer having a primary winding and a secondary winding, the primary winding of the first transformer being in series connection with the first port of the interface device; and a second transformer having a primary winding and a secondary winding, the primary winding of the second transformer being in series connection with the second port of the protection device, where the secondary winding of the first transformer is in parallel connection with the secondary winding of the second transformer.
In order to more clearly delineate the above and other features and advantages of the present invention, a further description with reference to the accompanying drawings is given below, wherein:
According to one preferred embodiment of the present invention, as schematically shown in
The interface device 202, as given in
The protection device 204, as given in
The high-impedance state of the interface device 202 and the protection device 204 can be formed by a tri-state circuit, for example, or other proper means.
For maintenance, the connection of the secondary winding of the transformer 302 and the secondary winding of the transformer 304 is placed on a separate module (a board, or card) 305.
In normal operation, the interface device 202 communicates with other device(s) through the transformer 302. The protection device 204 is controlled not to function to replace the communication of the interface device 202, and the port in series connection with the primary winding of the transformer 304 is in the high-impedance state as mentioned above. Thus, although connected in parallel with the secondary winding of the transformer 302, the secondary winding of the transformer 304 will not affect the normal communication.
If the interface device 202 fails to communicate, the port in series connection with the primary winding of the transformer 302 will be switched to the high-impedance state as mentioned above. The protection device 204 will be controlled to immediately replace the communication of the interface device 202 through the transformer 304. Since the port in series connection with the primary winding of the transformer 302 is in the high-impedance state, the secondary winding of the transformer 302 will not affect the communication occurring at the secondary winding of the transformer 304.
Compared to
Other details for the above preferred embodiment should be obvious to those skilled in the art, particularly to those skilled in the art of digital communication systems.
Although the present invention has been described in detail with reference to the above-illustrated particular embodiments, it is not intended that such particular embodiments be considered as limitations upon the scope of the present invention except in-so-far as set forth in the following claims.
