Terminal Landing Switch: Deceleration Ramp Trigger, Independent of Encoder, Terminal Floor Stopping and Commissioning Test

Terminal landing switches (also called slowdown switches, terminal deceleration switches, or final floor slowing switches) are proximity or magnetically-actuated switches mounted in the hoistway near the terminal floors. Function: (1) When the car approaches a terminal landing at high (rated) speed, the terminal switch triggers the controller to begin the deceleration ramp and register the terminal floor as the next stop; (2) Without terminal switches, a high-speed car running to the top or bottom could overshoot and trigger the final limit switch or buffer; (3) Terminal switches are typically set at a distance from the terminal floor equal to the braking distance at rated speed plus a safety margin; (4) They must be independent of the normal floor selector/position encoder so that even if the encoder fails, the terminal switch still enforces deceleration; (5) In variable-speed drives, the terminal switch typically switches the drive from full-speed profile to landing approach profile. Unlike the final limit switch (a safety circuit element), the terminal switch is a normal control function that operates on every run to a terminal floor. EN 81-20 Cl. 5.6 requires terminal stopping devices. The terminal switch is also used in testing to confirm that car deceleration at terminals is correct (commissioning test). Two terminal switches per direction are common: a pre-slowdown switch (earlier) and a close slowdown switch (nearer the floor).

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