| 摘要 |
In order to night-extinguish selected lamps (P<uN>u) in a row of street lamps (P) a short DC signal is applied to the AC power supply wires (F<u1>u, F<u2>u), whereby respective detector receivers (M) in the single selected lamp units (P<uN>u), e.g. every second lamp in the row, are caused to actuate a switch (30) for the respective lamps. A DC signal will be effective for this purpose, while an AC signal of high frequency would be strongly attenuated because of the condensers as commonly used in modern lamp units. The use of DC signals may show the problem that during the switching on phase of the lamps the ohmic resistance is very low, whereby the DC signal would be more or less suppressed by a relighting of the night-extinguished lamps, if the DC current was not otherwise unacceptably high; according to the invention, however, the relighting is caused to take place only after termination of the DC signal. A plurality of separately power supplied rows of lamps may be operated for partial night-extinguishing by the DC signal on a first row being utilized for actuation of a DC signal generator in a following row, and so forth.
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