Car Door Lock: Safety Circuit Contact, Direct-Opening, Movement Prevention Open Door and Distinction from Landing Door Interlock

The car door lock (car door contact, CDC) is an electrical safety contact — and in some configurations also a mechanical lock — installed on the car door that forms part of the safety circuit. EN 81-20 Cl. 7.7.3 requires that when a car door is provided, it must have a contact or lock verifying closure before movement. Operation: (1) When the car door is open or not fully closed, the car door contact is open, breaking the safety circuit and preventing any car movement; (2) The contact must be a direct-opening type (not held closed by spring force alone); (3) It is wired in series with all other safety circuit contacts; (4) The contact actuates on car door closure — typically through a cam and roller mechanism on the door panel and car frame. Distinction from landing door interlock: the car door contact only verifies that the door is closed (mechanical locking is not always required on car doors in EN 81-20, as the primary shear hazard is at the landing door); however, ASME A17.1 (North American code) requires a car door interlock with both electrical and mechanical locking. Car door contacts are also part of the door reopening logic: if the door is obstructed and does not fully close, the safety circuit remains open, the reopening device re-opens the door, and the car cannot move. Car door contacts are tested at commissioning and periodic inspection.

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