Communications: electrical – Systems – Selsyn type
Patent
1997-03-10
1999-07-06
Crosland, Donnie L.
Communications: electrical
Systems
Selsyn type
34031002, 34031006, 375259, H04B 100, H04L 2700
Patent
active
059202530
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a local area network arrangement in accordance with the preamble of the attached claim 1. Unlike with conventional local area networks, in which performance (data transfer rate) is of importance, the local area network-of the invention is specifically intended for bidirectional transmission of slow data, in particular for bidirectional transmission of switch information (ON/OFF). The local area network arrangement of the invention is primarily developed for mains power control of real estates, but it also has other remarkable uses, such as access control systems and other monitoring or control systems. In the following, however, the background of the invention will be described with reference to an example of a mains control system of a real estate, as problems related to it have originally given an impulse to the invention.
2. Description of the Related Art
The greatest drawback of real estate electrification implemented in the conventional way is the fact that it does not enable "intelligent" installation that would allow flexible control and variability of the system. FIG. 1 illustrates the principle of the conventional installation technique. A separate conduit usually leads from a main distribution board 11 for each group of light fittings or wall sockets. In the figure, the number of the wires required is indicated with a number marked beside the cross line drawn across the wire, as usual; 2 or 3 wires are led to a switch 13 from each light fitting 12, and two wires are required for each group. In the example shown in the figure, a total number of 8 wires thus lead to the main distribution board (wall sockets are marked with reference number 14). An installation of this kind is simple, but also extremely fixed, and requires a professional for making modifications.
BRIEF SUMMARY AND OBJECTS OF THE INVENTION
For achieving controllability, a relay-controlled installation technique must be used, the principle of which is illustrated in FIG. 2. As the switches (relays) of all the outlets (e.g. light fittings) to be controlled are in this case situated in the main distribution board 11, as many wires must lead outwards from the distribution board, as there are outlets to be controlled in the building. As typically three or four wires are required for each push-button (switch) 15 equipped with a signal light, the number of wires going out from the main distribution board will be very large. For instance, electrification of a typical detached house requires a number of 25 . . . 50 push-buttons equipped with a signal light, in which case from these buttons alone, 75. 200 wires lead to the main distribution board. As to the number of wires, the relay-controlled installation technique thus mainly resembles a telephone exchange. Furthermore, it requires a highly experienced electrician, the installation time rises remarkably long, and the costs rise extremely high.
The object of the present invention is thus to achieve an improvement to the above-mentioned drawbacks, and provide such a local area network arrangement that enables a flexible, distributed control system, which may be implemented in a much more simple manner than the prior system. This object is achieved with the local area network arrangement of the invention.
The idea of the invention is to convey in a bus (twin cable) of the network such a signal that ensures a similar response time to all control functions, and at the same time enables a simultaneous bidirectional data transmission and power feed, so that an individual node of the network may be kept (e.g. in terms of timing, and transmitter devices) as simple as possible. When one half of a carrier signal cycle (which signal is substantially sinusoidal in its basic form in accordance with a preferred embodiment of the invention) is entirely preserved from power feed, it is possible to transfer data in two directions during it. This may be applied in a very simple manner in one direction on the basis of current in
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