Elevator systems

An elevator system (102) comprising:

• a plurality of hoistway doors (10a, 10b, 10c) and
• a corresponding plurality of sets of non-contact switches (112a, 112b, 112c), each set arranged to detect when a respective hoistway door (10a, 10b, 10c) is open;
• and
• a monitoring device (126);
• wherein each set of non-contact switches (112a, 112b, 112c) comprises:
• a first non-contact switch (114a, 114b, 114c) arranged to open when the respective hoistway door (10a, 10b, 10c) is open;
• a first impedance (118a, 118b, 118c) connected in series with the first non-contact switch (114a, 114b, 114c);
• a second non-contact switch (116a, 116b, 116c) arranged to open when the respective hoistway door (10a, 10b, 10c) is open;
• and
• a second impedance (120a, 120b, 120c) connected in series with the second non-contact switch (116a, 116b, 116c);
• wherein the first non-contact switch (114a, 114b, 114c) and the first impedance (118a, 118b, 118c) are connected in parallel with the second non-contact switch (116a, 116b, 116c) and the second impedance (120a, 120b, 120c);
• wherein the sets of non-contact switches (112a, 112b, 112c) are connected in series to form an electrical path (122);
• and
• wherein the monitoring device (126) is arranged to measure an electrical property of the electrical path (122) to detect when a hoistway door (10a, 10b, 10c) is open.

An elevator system (202) comprising:

• a plurality of hoistway doors (10a, 10b, 10c) and
• a corresponding plurality of sets of non-contact switches (212a, 212b, 212c), each set arranged to detect when a respective hoistway door (10a, 10b, 10c) is open;
• and
• a monitoring device (226);
• wherein:
• each set of non-contact switches (212a, 212b, 212c) comprises at least one non-contact switch (214a, 214b, 214c), and at least one further electronic component (218a, 218b, 218c, 220a, 220b, 220c) connected in parallel with the non-contact switch (214a, 214b, 214c) so that each set of non-contact switches (212a, 212b, 212c) comprises a unique AC electrical property;
• the sets of non-contact switches (212a, 212b, 212c) are connected in series to form an electrical path (222);
• and
• the monitoring device (226) is arranged to measure an AC electrical property of the electrical path (222) to detect and identify an open hoistway door (10a, 10b, 10c).