Modern elevators rely on many layers of protection. Some devices stop the car, some prevent doors from closing on people, and others protect the equipment itself. Knowing what each device does helps technicians, building owners, and passengers understand how elevators stay safe.
How the Safety System Works Together
Most safety devices are wired in series in a safety circuit. If any one device opens (for example, a door lock, a stop switch, or the governor switch), the circuit breaks and the motor and brake de-energize, so the car stops.
Mechanical devices, such as safety gear and buffers, act as a last line of defense if electrical protection fails.
Safety devices should never be bypassed, jumpered, or disabled except by an authorized technician following a documented procedure, and only for as long as the task requires.
Good protection comes from layers: prevention (limit switches, interlocks), detection (governor, sensors), and last-resort mechanical action (safety gear, buffers).
Equipment Protections
The elevator control system guards against these electrical and mechanical faults:
Overload: prevents the car from running when the load exceeds its rated capacity.
Voltage fluctuations: protects the equipment from unsafe supply variations.
Overspeed: detects excess speed and stops the car.
Phase reversal: prevents the motor from running if the supply phase sequence is wrong.
Phase failure: stops the motor if one or more phases of the supply are lost.
Motor overheating: thermal sensors or overload relays stop the motor before it is damaged.
Short circuit and overcurrent: circuit breakers (MCBs/MCCBs) and fuses disconnect faulty circuits.
Earth leakage: residual current devices (RCD/ELCB) cut the supply if current leaks to earth, reducing shock risk.
Overload indication: a buzzer or light warns passengers and keeps the doors open until the excess load is removed.
Preventing Free Fall and Overspeed
No.
Device
Function
01
Overspeed governor (OSG) and safety gear
Prevents the car from free-falling in the down direction. Operates when the speed exceeds the set limit (110% of rated speed in your draft). Breaks the safety circuit and stops the motor when it activates. Safety gear can be instantaneous or progressive.
02
Safety gear on the counterweight (not common)
Prevents the counterweight from free-falling. Operates when the speed exceeds the set limit and breaks the safety circuit.
03
Buffers
Stop the car or counterweight if it travels past the lowest landing, absorbing the impact with a spring or oil. The terminal limit switch breaks the safety circuit.
04
Counterweight guard
Keeps the weights from falling out of the frame when the counterweight hits the buffers.
05
Governor rope and tension pulley
Connects the governor to the car and keeps the rope taut so that the safety gear is pulled correctly when the governor trips.
06
Governor rope tension switch
Breaks the safety circuit if the governor rope slackens, stretches, or breaks.
07
Buffer compression switch (oil buffers)
Confirms the buffer has returned to its normal extended position after use, and prevents the car from running if it has not.
08
Ascending car overspeed protection
Stops the car if it moves up too fast, for example, if the counterweight is heavier than the car and the brake fails. Common on modern elevators.
09
Unintended car movement protection
Detects the car moving away from the landing with the doors open and stops it, for example, using a rope gripper, safety gear, or a brake acting on the machine.
Brakes and Drive Protection
No.
Device
Function
10
Machine brake
Holds the car at rest and stops it when power is removed. It is spring-applied and electrically released, so it engages on power loss.
11
Dual or redundant brake system
Uses two independent brake circuits so that one can still stop and hold the car if the other fails.
12
Rope gripper
Grips the suspension ropes or traction sheave to stop the car in overspeed or unintended-movement cases.
13
Slack rope or slack chain switch
Breaks the safety circuit if the suspension ropes or compensating chains go slack, which can happen when the car or counterweight lands on an obstruction.
14
Suspension ropes with a safety factor
Ropes are sized with a high safety factor and are monitored for wear, broken wires, and corrosion.
15
Drive and controller fault monitoring
Detects drive faults, encoder faults, and speed deviations, and stops the car safely.
Travel Limit Protection
No.
Device
Function
16
Synchronization switch
Located at the extremes of the shaft, near the deceleration level. Slows the elevator and updates its position when operated.
17
Stop limit switch
Located at the extremes of the shaft, about 30 mm from the floor level. Stops the elevator in one direction when operated. Provided for service personnel safety.
18
Final limit switch
Located beyond the stop limit switch at the extremes of the shaft. Breaks the safety circuit when operated before the car reaches the buffers.
19
Terminal slowdown switches
Force the car to slow down as it approaches the top and bottom terminals, even if the normal control fails.
20
Overtravel clearance and mechanical stops
Top and bottom clearances in the shaft keep a safe space for people and let the car stop without hitting the overhead or the pit floor.
Door Protection
No.
Device
Function
21
Car door lock
Operates at 230 VAC. The car moves only when the contact is closed. A mechanical lock is provided for special cases.
22
Electromechanical lock for landing doors
Locks the landing door when it is shut and makes the electrical contact (230 VAC). Prevents the door from being opened from outside and opens only when the car is at the landing. It can be opened from outside with an emergency key.
23
Electrical lock for landing doors
Uses a shorting piece located on the other door panel. Makes the electrical contact when the door shuts (230 VAC).
24
Pressure limiter (door force limiter)
Senses when the pressure during door closure exceeds a set value and stops the door from closing further.
25
Photocell
Provides additional protection by preventing the doors from closing when someone is between them.
26
Infrared light curtain
Senses passenger movement or obstruction on automatic doors. As soon as it detects something, the doors reverse and stay open, helping prevent collisions and door jamming.
27
Safety edge (mechanical door reopening device)
A contact strip on the leading edge of the door. If it touches a person or object, the doors reverse.
28
Door-closing speed and kinetic energy limit
Limits the door’s closing force and speed so that contact with a passenger does not cause injury.
29
Door zone and pre-opening detection
Detects that the car is within the door zone, so the doors can open only when the car is at or near the landing.
30
Door lock monitoring
Checks that the car and landing door locks are truly closed and locked before the car can move.
31
Door-open timer and nudging
Keeps the doors open for a set time and closes them with a warning buzzer if they are held open too long.
Stop Switches and Maintenance Controls
No.
Device
Function
32
Pit stop switch
Located in the pit (one or two switches). Breaks the safety circuit when operated (230 VAC).
33
Car stop switch
Located in the car operating panel (COP) (230 VAC). Stops the elevator immediately when pressed.
34
Car top stop switch
A stop switch on the car top that lets a technician cut power before working.
35
Inspection control station
A set of controls on the car top (and sometimes in the pit) that allows slow-speed travel for maintenance and that disables normal operation while in use.
36
Machine room and pulley room stop switch
Allows a technician to stop the elevator from the machine area.
37
Main isolator or disconnect switch
Cuts the main power supply and can be locked out and tagged out for safe work.
38
Pit ladder and pit lighting
Provide safe access and visibility for technicians working in the pit.
39
Refuge space and mechanical props
Provide a safe space in the pit or on the car top and mechanical blocks that hold the car up while technicians work under it.
Car Protection
No.
Device
Function
40
Car top guardrail
Prevents technicians from falling off the car top when the shaft clearance and design require it.
41
Emergency exit hatch with electrical contact
Allows rescue personnel to exit through the car top. Opening it breaks the safety circuit so the car cannot move.
42
Handrails and car interior protection
Give passengers support, and protect from sharp edges and loose panels.
43
Ventilation fan and lighting
Keep the car comfortable and lit during normal use.
44
Load weighing device
Measures the car’s load and prevents operation when overloaded, and also helps the controller skip landings when the car is full.
Emergency and Rescue Systems
No.
Device
Function
45
Intercom
Runs on a separate inverter supply (24 VDC). Let trapped passengers talk to someone outside where the receiver unit is kept.
46
Emergency alarm
Runs on a separate inverter supply (24 VDC). Let trapped passengers call for help.
47
Emergency light
Runs on a separate inverter supply (230 VAC). Keeps the car lit during a power failure.
48
Rescue device
Operates during a power or system failure. Brings the elevator to the nearest floor and opens the door, powering the motor from maintenance-free batteries.
49
Manual rescue operation
Let trained personnel release the brake or turn the machine by hand to move the car to a landing when power and automatic rescue are not available.
50
Remote monitoring and alarm systems
Send fault and entrapment alerts to the service provider or building management.
51
Fire service operation
Recalls the car to the designated floor when the fire alarm activates and gives firefighters manual control.
52
Seismic sensors
In earthquake-prone areas, they detect shaking and send the car to the nearest landing or stop it safely.
53
Backup power or generator connection
Allows elevators to continue to operate, or to complete a rescue run, during a power outage.
Hydraulic Elevator Safety Devices (new)
No.
Device
Function
54
Pressure relief valve
Limits maximum system pressure and protects the pump, piping, and jack.
55
Rupture (pipe burst) valve
Closes if the hydraulic pipe or hose fails so that the car cannot fall quickly.
56
Manual lowering valve
Allows trained personnel to lower the car to a landing during a power failure.
57
Hand pump
Allows the car to be raised manually in an emergency.
58
Oil temperature and level monitoring
Prevents the system from running if the oil is too hot or too low.
59
Down-travel timer or motor run-time limiter
Stops the pump if the motor runs longer than expected, which can show a leak or a stalled car.
Electrical Protection
No.
Device
Function
60
Earthing (grounding)
Prevents electric shock. All components are earthed as required.
61
Phase sequence relay
Prevents operation if the supply phases are reversed or missing.
62
Surge protection
Protects electronic controllers and drives from voltage spikes.
63
Insulation and cable protection
Proper insulation, cable trays, and guards prevent wear, short circuits, and contact with live parts.
Testing and Maintenance of Safety Devices
Test safety devices on a schedule set by the manufacturer, the local code, and your company procedure.
Check door locks, contacts, and safety edges at every service visit.
Test the governor, safety gear, and buffers at the intervals required by your code, and after any repair or adjustment.
Check brake wear, brake release, and holding torque regularly.
Test emergency lighting, intercom, alarm, and rescue device batteries regularly.
Inspect ropes for broken wires, wear, corrosion, and uneven tension.
Check limit switches for correct position and operation.
Keep records of every test, defect, and repair.
Never leave a safety device bypassed, and remove all jumpers before returning the elevator to service.
Take the elevator out of service if a critical safety device fails a test.
Warning Signs of Safety Device Problems
Doors that reopen repeatedly, stick, or do not close fully.
The car stops at the wrong level or overshoots the floor.
Jerky starts or stops, or unusual vibration.
Grinding, squealing, or knocking noises.
Burning smells or visible smoke.
Alarm, intercom, or lighting not working.
Frequent faults or tripping of breakers.
Oil leaks in hydraulic elevators.
Report any of these to building management or the elevator contractor right away, and do not use the elevator if you think it is unsafe.
What Passengers Should Know
Never try to force doors open or hold them with objects.
Never push the alarm button as a joke, because it ties up emergency response.
If the elevator stops, use the alarm or intercom, and wait for trained help.
Do not exceed the posted load limit.
Report a damaged or unusual elevator to building management.
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