“Draw gate-level logic for elevator fire service recall using FIRE_ALARM, alternate recall selection, main and alternate recall positions, and DOOR_CLOSED inputs to produce RECALL_MAIN, RECALL_ALT, and HOLD_DOORS outputs.”
Read the decisions behind it.
Alternate selection inhibits the main recall request.
Motion is only enabled while the door is closed.
The selected recall output stays off once that landing is reached.
Door hold asserts when the car is at the selected recall landing.
This diagram illustrates boolean relationships only. Fire service operation must be designed and approved to the applicable elevator and fire alarm standards by qualified professionals.
Other examples in this family.
Common questions
What is alternate recall?
It is an alternate landing selected when the primary recall floor is unsuitable.
Why require a closed door for recall motion?
The example models a basic interlock so movement is not commanded with an open door.
Can this circuit be used in a real lift?
No. Real fire service controls require certified, code-compliant equipment and design.