Function

A simpler structure is hardly conceivable for a four door vehicle. Neither the trunk nor the petrol cap are included into the system. Using radio remote maintenance or keyless entrance the control unit would have to be substantially extended. The system represented above is rather meant for equipping a used vehicle. But the schematic diagram shows the basic functions of the central locking device quite well...

How it works

Starting on the top left, we catch the voltage supply and fuses. Besides (in reality very small) there is the control unit with two power relays to its right for switching and reversing the polarity of the engines. The next row contains the engines for the front followed by the engines for the rear doors in the last row. The engines at the front doors have limit switches as sensors for the control unit. They can be operated also using the key.
Such a procedure can be simulated with the switching surfaces. On the basis of four opened doors the driver' s door is locked. The positions of the limit switches changes. Thereupon the control unit pulls the left relay. All remaining engines go into closing position. Once this is accomplished, the control unit switches off the power supply. When opening the procedures are similar. However, the power relays to the right are being used. All actions can be taken from the passenger door, too.

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