Door Operators & Interlocks Flashcards
7 cards from real CET practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Door Operators & Interlocks flashcards as text
What is the purpose of a door operator encoder (or resolver) on a modern microprocessor-based door system?
Answer: Provides real-time door panel position feedback to the controller for precise speed and position control
An encoder or resolver provides precise feedback on door panel position and velocity, allowing the microprocessor to execute accurate velocity profiles for smooth, controlled door operation.
Which of the following conditions would cause a 'door open fault' on a microprocessor-based door operator during a closing cycle?
Answer: The door fails to reach the fully closed position within the allotted time
A door open fault is triggered when the door fails to complete its travel to the fully closed position within the controller's preset time window.
A technician is measuring interlock contact resistance and reads 4 ohms across a closed interlock contact. This reading indicates:
Answer: Excessive contact resistance indicating dirty, pitted, or worn contacts needing service
Closed interlock contacts should measure nearly zero resistance; a reading of 4 ohms indicates corrosion, pitting, or wear that increases resistance and can cause erratic safety circuit behavior.
On a freight elevator with a bi-parting vertical-slide (freight) door, the interlock is typically located:
Answer: At the top of the upper door panel where the locking bolt engages
On bi-parting vertical freight doors, the interlock locking mechanism is typically located at the top of the upper (or lower) door panel where the bolt engages a keeper as the door reaches the closed position.
What is the maximum force required to open a manually operated hoistway door from the landing side using a drop (tri) key?
Answer: 30 lbs
ASME A17.1 requires that a hoistway door equipped with a manual door closer must be openable with a drop key using no more than 30 lbs of force when within the unlocking zone.
When troubleshooting a door that reopens immediately after starting to close, which component should be checked FIRST?
Answer: Safety edge or light curtain and its wiring for a false activation signal
Immediate reopening during closing typically indicates the reopening device (safety edge or light curtain) is sending a continuous or false obstruction signal, which should be investigated first.
According to ASME A17.1, the electrical contact portion of a hoistway door interlock must be designed so it cannot be held in the closed position by:
Answer: Spring pressure alone without mechanical locking
ASME A17.1 requires that the interlock electrical contact cannot be maintained in the closed position by spring pressure alone — a positive mechanical lock must hold the contact closed.