Pulse or digital communications – Cable systems and components
Reexamination Certificate
1999-03-15
2003-04-22
Chin, Stephen (Department: 2734)
Pulse or digital communications
Cable systems and components
C375S219000
Reexamination Certificate
active
06553076
ABSTRACT:
This invention relates, in general, to the field of wired digital control network systems. In particular, this invention relates to a wired communication and control network system and a method for avoiding collision in the transmission of data in such a system.
BACKGROUND OF THE INVENTION
Home and building automation is an important area in the development of modern technology, of which the design of control systems is one of its crucial areas. Many proposals have been put forward in this field, e.g. “X-10”, “Lonwork”, “CEBus” and “EIB”.
Home and building control systems are complicated and multi-faceted systems. Stand-alone or point-to-point products clearly cannot fulfill the various requirements which may arise in real life situation. A control network system is much more versatile and may therefore meet such requirements. The nodes in such a control network system can communicate with one another, share the same resources, and be assembled together by various means (e.g. switches, sensors, timers, telephones, computers, etc.) in the light of the needs, in order to realize various control functions, e.g. integrated control and monitoring of lighting, energy, access and security at home or office.
Centralized control system is a well-known technology. However, the application of such a technology in home and building automation has met with various problems, e.g. complicated wiring (due to the large number of wires required), difficulty in extending the system (as there is usually a fixed capacity for each central control system), space requirement (due to the need to accommodate the central unit usually in a separate room), and the rigorous requirements for reliability (e.g. the whole system will not function when there are problems with the central unit).
At present, there are many media access control (MAC) methods, e.g. token passing, polling, circuit switching, and time-division multiple access (TDMA), etc. However, to a control network, while the signals/data to be transmitted arc usually relatively short, the response speed is required to be relatively high. Random access is thus one of the few methods which can meet the requirements of a real-time control.
In a random access system, it is possible that more than one node seek to transmit signals/data at the same time, resulting in a collision. Various methods have been devised to resolve such contentions, to recover from collisions, or to avoid collisions. Such methods include CSMA/CD (Carry Sense Multiple Access with Collision Detection) and CSMA/CA (Carry Sense Multiple Access with Collision Avoidance). However, irrespective of the method used, if two or more nodes transmit signals/data at the same time, all such attempted transmissions will fail. Each of these nodes has to stop transmitting for a respective period of time, and tries transmitting again. Such will cause a reduction of the communication efficiency.
Most current communication networks do not consider the issue of priority. If the data packets to be transmitted are not queued sequentially, each has to wait for the same pre-determined period of time before it is transmitted. This is a conventional method for, and does not cause much difficulty to, a communication system. However, the issue of priority becomes very important to a control system. The difference could be very significant since different nodes may carry out different functions within the system. In case of emergency, serious problems may arise if certain important signals/data cannot be transmitted by a particular node.
To a wired control network, it is desirable to keep the number of wires to a minimum. The more are the number of wires, the more inconvenient the wiring process will be, and the higher the risk of mis-wiring will also be. For example, even in a network in which there are only four wires (e.g. USB), there are 23 (i.e. (4!-1)) ways of mis-wiring.
While it is a common practice to provide a separate power source for each node in the network, it is desirable to provide electric power to the nodes through the network. Common link power systems generally adopt transformer coupling to separate power from signals in the bus/transmission medium. Because of the use of transformers, the system is usually of a relatively large size, and thus more expensive. In addition, due to the relatively low internal resistance of the transformer, the fanning-out capacity of the bus/transmission medium will be lowered when the transformer is connected to the network.
It is thus an object of the present invention to provide, a mixed mode transceiver digital control network system, a transceiver, a method of setting priority to each node, and a method for avoiding collision in such a system, in which the aforesaid shortcomings are mitigated, or at least to provide a useful alternative to the public.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention, there is provided a digital data communication network system including a power supply means and at least two nodes, wherein said power supply means and said nodes are connected to one another via a transmission media whereby-digital signals/data are transmittable between said nodes, wherein said power supply means supplies electric power to said nodes, and wherein at least one of said nodes includes a current mode transmitter and at least one of said nodes includes a voltage mode receiver. This aspect of the invention has a number of independent sub-aspects. In one sub-aspect the system includes a pulse generating means through which electric current from said power supply means passes to induce a voltage pulse. In another sub-aspect the voltage mode receiver includes a capacitor and an inverter means.
According to a second aspect of the present invention, there is provided a digital data communication system for delivering digital signals from a current mode transmitter to a voltage mode receiver, said system including an electrically conductive cable coupling said transmitter and said receiver with each other, thereby providing a digital data communications path; DC power supply means for producing a pre-determined electric potential, said power supply means having a first voltage terminal and a second voltage terminal; current control means coupling said first voltage terminal of said power supply means to said cable for providing a first electric current path, said first electric current path operating as a low impedance path for DC current; voltage control means connected in parallel with said current control means for controlling the voltage amplitude across said current control means, and for providing a second electrical path for transient electric current; connecting means coupling said second voltage terminal of said power supply means to said cable to provide a power distribution path; wherein said current mode transmitter is coupled to said cable for implementing a current loop, wherein said transmitter produces current pulses in said current loop to perform a current mode digital data transmission; and wherein said voltage mode receiver is coupled to said cable for receiving voltage pulses on said cable produced by said voltage control means to perform a voltage mode digital data reception.
According to a third aspect of the present invention, there is provided a digital data communication network system for distributing power and for providing signal passing capabilities through a bus, said network including a plurality of nodes each including a mixed mode data bus transceiver for generating electric current pulses and receiving electric voltage pulses; an electrically conductive cable coupling said nodes with one another to provide a path for power delivery and data communications; a DC power supply means for producing a pre-determined electric potential, said power supply means having a first voltage terminal and a second voltage terminal; current control means coupling said first voltage terminal of said power supply means to said cable for providing a first DC current low impedance path; voltage control
Actpro International Limited
Chin Stephen
Fan Chieh M.
Hall Priddy Myers & Vande Sande
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