What is Door Lock Monitoring?

Where does the phrase “𝗗𝗼𝗼𝗿 𝗟𝗼𝗰𝗸 𝗠𝗼𝗻𝗶𝘁𝗼𝗿𝗶𝗻𝗴” come from?

The phrase “𝗗𝗼𝗼𝗿 𝗟𝗼𝗰𝗸 𝗠𝗼𝗻𝗶𝘁𝗼𝗿𝗶𝗻𝗴” does not appear anywhere in the code—it does not exist.

Instead, door lock monitoring, abbreviated as “DLM,” is the nickname given to the functionality described in ASME A17.1 Safety Code for [New] Elevators and Escalators in Section 2.26.5 and ASME A17.3 Safety Code for Existing Elevators and Escalators in Section 3.10.12

The DLM functionality is described in the code as a “System to Monitor and Prevent Automatic Operation of the Elevator with Faulty Door Circuits”—that’s a mouthful. It’s too long to remember and too many words to say easily.

People needed a shorter name and a better way of describing it. But where did the phrase “𝗗𝗼𝗼𝗿 𝗟𝗼𝗰𝗸 𝗠𝗼𝗻𝗶𝘁𝗼𝗿𝗶𝗻𝗴” come from?

Under the code, the elevator must follow two sets of requirements for DLM functionality. The name “𝗗𝗼𝗼𝗿 𝗟𝗼𝗰𝗸 𝗠𝗼𝗻𝗶𝘁𝗼𝗿𝗶𝗻𝗴” comes from the second set of requirements:

From ASME 17.1 Section 2.26.5:

“(b) prevent the power closing of the doors during automatic operation if the car door is fully open and any combination of the following conditions exist:

(1) the car door closed detection means has detected the closed position or the car door interlock detection means has detected the closed and locked position

(2) the door locked detection means of the landing door that is coupled to the opened car door has detected the closed and locked position, except as required in 2.27.3.3.9

(3) the portions of the circuits incorporating the closed detection means or door locked detection means of the car door or landing door that is coupled to the opened car door are bypassed.”

In other words, a key portion of this code ensures that the door locks are monitored to ensure they are not shorted, bypassed, worn out, or malfunctioning. While this is not 100% of the code’s requirements, it is enough to merit the phrase “𝗗𝗼𝗼𝗿 𝗟𝗼𝗰𝗸 𝗠𝗼𝗻𝗶𝘁𝗼𝗿𝗶𝗻𝗴” as a nickname.