Communications: electrical – Systems – Selsyn type
Patent
1980-07-11
1983-10-04
Caldwell, Sr., John W.
Communications: electrical
Systems
Selsyn type
340310R, 34082554, 307 3, H04M 1100, H04Q 500
Patent
active
044081855
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for transferring information between electrical devices interconnected via at least two power supply lines through which an alternating supply current flows, said lines being also used for transferring information between the electrical devices.
The German Offenlegungsschrift No. 2 428 173 discloses a technique by means of which the supply current to a plurality of electrical devices is essentially cut off in one or more subsequent halfwave intervals to thereby transfer information to the electrical devices which have means for detecting one or more missing halfwaves.
This technique suffers from the drawback that certain forms of loads do not function satisfactorily when the supply current is cut off for the duration of a halfwave interval. For example, lamps show an inconvenient flicker in this technique. This drawback is particularly pronounced when a high rate of information is desired which implies cutting away many halfwaves in a predetermined, relatively dense pattern. Another disadvantage of said technique is that the maximum rate of information is limited by the frequency of the supply current.
The object of the invention is to provide a process making it possible to transfer information on the power supply lines without said drawbacks.
This object is achieved in that, depending upon a first type of information to be transferred, current flow through the power supply lines is blocked fully or partially in positionally determined periods constituting a fraction of a halfwave interval, and in that one or more of the devices transmit a second type of information on the power supply lines at least in some respective ones of said periods in which, as opposed to the first type of information, the second type of information is not dependent upon the frequency of the current supply.
By cutting-off current only for a fraction of a halfwave interval and preferably adjacent a current zero-crossing, the reduction in power supply during the transfer of the first type of information will be significantly smaller than the reduction in power caused by the prior art. The rate of information of the second type of information is not limited by the frequency of the current supply, so information may be transferred at a great velocity on the power supply lines themselves, i.e. without the use of special data lines, because the second type of information is transmitted during the periods in which the current supply source is disconnected. The current supply source will accordingly not act as a load on the transmission of the second type of information which may therefore be effected with a significantly lower consumption of power than would normally be required.
Blocking of a power supply line is normally initiated at a time which is synchronized with the zero-crossing of the supply current, and as allowance must be made for the possibility of a certain phase displacement between current and voltage on the power supply lines, the periods in which the power supply lines are disconnected may become unnecessarily long if blocking is ended a predetermined time after the zero-crossing of the supply voltage. Ending of said blocking a predetermined time after the zero-crossing of the supply current allows a necessary and sufficient duration of the periods to be achieved in which the power supply line is disconnected. Another advantage is that the duration of said periods is well-defined which means that the second type of information may be transmitted during the entire period mentioned.
The invention also relates to a system for carrying out the process, said system being characterized by the fact that it comprises change-over means arranged to cut off, in response to a first type of information, current flow in positionally determined periods which constitute a fraction of a halfwave interval, and that at least some of the devices have detector means for positional determination of said periods and have control means and transmission means arranged to transmit a second type of information o
REFERENCES:
patent: 3462756 (1969-08-01), Mills
patent: 3488517 (1970-01-01), Cowan et al.
patent: 3525078 (1970-08-01), Bassott
patent: 3594584 (1971-07-01), Woods
patent: 3714451 (1973-01-01), Whitney et al.
patent: 3818466 (1974-06-01), Honda
patent: 4106007 (1978-08-01), Johnston et al.
patent: 4254403 (1981-03-01), Perez et al.
Caldwell Sr. John W.
Crosland Donnie L.
Elsmark A/S
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