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Local control system for domestic appliances and alarm devices

  • US 4,899,131 A
  • Filed: 11/23/1987
  • Issued: 02/06/1990
  • Est. Priority Date: 04/07/1986
  • Status: Expired due to Fees
First Claim
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1. In a local control system for system loads, comprising a central unit and a two-wire bus line interconnecting the central unit and the system loads, wherein the system loads are connected to the bus line via terminal units which are responsive to a voltage signal emitted by the central unit and being unique with respect to a respective terminal unit for applying a control signal to a predetermined system load, the central unit being connected to apply a DC voltage to the bus line for supplying operating power to the respective terminal unit and system loads connected to the system, the central unit comprising means for detecting changes in the bus line current and for determining the status of a system load from said changes, the improvement wherein said central unit comprises means for emitting a first signal unique to a respective terminal unit and followed by an additional signal, said respective terminal unit comprising means responsive to the first signal for transferring said additional signal to an output of the terminal unit, and further comprising a manual control unit connected to said output, said manual control unit comprising a keyboard having keys and including means responsive to depression of said keys for varying current flowing in said bus line, said central unit being responsive to variation in said current in said bus line for applying a signal including said first and additional signals to said terminal unit said additional signal operating to identify the key being pressed.

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