Abstract: A method for preventive maintenance of an elevator speed sensor system includes at least a first and a second sensor, which are independent of each other. The method includes: determining a reference distance for an elevator car travel between a first door zone and a second door zone, during the elevator car travel, defining continuously a first elevator car speed information from the first sensor and a second elevator car speed information from the second sensor, calculating a cumulative sensor system error by integrating the difference between the first elevator car speed information and the second elevator car speed information, and dividing the cumulative sensor system error with the reference distance to obtain a sensor system performance indicator.

Abstract: According to an aspect, there is provided a communication system for transmitting safety information in an elevator system. The communication system comprises a first node; and a second node ; wherein the first node is configured to receive first safety information from a first safety node via two parallel communication channels, to convert the received first safety information into a serial form for transmission in a first safety message over a single communication channel between the first node and the second node and to transmit the first safety message to the second node over the single communication channel; and the second node is configured to receive the first safety message and to convert the first safety information in the first safety message back into the parallel form for transmission via two parallel communication channels to a second safety node.

Abstract: A method for preventive maintenance of an elevator speed sensor system includes at least a first and a second sensor, which are independent of each other. The method includes: determining a reference distance for an elevator car travel between a first door zone and a second door zone, during the elevator car travel, defining continuously a first elevator car speed information from the first sensor and a second elevator car speed information from the second sensor, calculating a cumulative sensor system error by integrating the difference between the first elevator car speed information and the second elevator car speed information, and dividing the cumulative sensor system error with the reference distance to obtain a sensor system performance indicator.