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Emergency terminal stopping devices shall be installed on all elevators with static control and rated speeds over 1 m/s (200 ft/min) and shall conform to 2.25.4.2.1 and 2.25.4.2.2, except for elevators with static generator-field control that use the normal terminal stopping device to limit the generator-field current directly, or elevators that have an emergency terminal speed-limiting device that complies with 2.25.4.1.
2.25.4.2.1
The emergency terminal stopping device shall cause power to be removed from the driving-machine motor and brake should the normal stopping means and the normal terminal stopping device fail to cause the car to slow down at the terminal as intended.
2.25.4.2.2
The emergency terminal stopping device shall function independently of the normal terminal stopping device and the normal speed control system such that the failure of the normal terminal stopping device and/or the failure of the normal speed control system shall not prevent the emergency terminal stopping device from functioning as specified, except that
(a) for both the position-sensing device of the emergency terminal stopping device and the position-sensing device of the normal terminal stopping device
(1) a common actuating means (e.g., a cam) that is not physically part of the position-sensing devices shall be permitted
(2) a common member (e.g., tape, target, or wire) that is sensed by both the emergency terminal stopping device and normal terminal stopping means shall be permitted, provided that both of the following apply:
(-a) the member is monitored such that when its presence is not detected, this shall cause the electric power to be removed from the elevator driving-machine motor and brake
(-b) the common member is securely mounted in such a manner that horizontal movement of the car shall not affect the operation of the sensors
(3) a common mounting means shall be permitted for the position-sensing devices of the emergency terminal stopping device and the normal terminal stopping device
(b) The car speed-sensing device used for the emergency terminal stopping device shall be permitted to be either a separate car speed-sensing device from that of the normal speed control system or the same car speed-sensing device, provided that a separate means is used to continuously verify the proper operation of this speed-sensing device. Where the same car speed-sensing device is used, the detection of a failure of this car speed-sensing device shall cause the power to be removed from the driving-machine motor and brake.
The car speed-sensing device(s) and, where required, the verification means described above, shall conform to the following:
(1) A common actuating means (e.g., a driving-machine shaft or brake drum) shall be permitted, provided that it is not dependent on any of the following connection types, unless the connection is continuously monitored:
(-a) traction (excluding the traction between the drive sheave and suspension means and the traction between the governor and governor rope)
(-b) friction (except for interference fits)
(-c) a flexible coupling where positive engagement is not assured between coupling halves
Where monitoring is required, the monitoring shall detect a failure that prevents conformance with this requirement and shall cause the electric power to be removed from the elevator driving-machine motor and brake.
(2) A common member (e.g., tape, target, or wire) that is sensed by both speed-sensing devices shall be permitted, provided that
(-a) the member is monitored such that when its presence is not detected, this shall cause the electric power to be removed from the elevator driving-machine motor and brake
(-b) the common member is securely mounted in such a manner that horizontal movement of the car shall not affect the operation of the sensors
(3) A common mounting means shall be permitted.

Related Code Sections

2.25.4.1.1 Electric Elevators,
If the normal terminal stopping device fails to slow down the car at the terminal as intended, the emergency terminal speed-limiting device shall ...
2.25.4.1.5 Electric Elevators,
The emergency terminal speed-limiting device shall be designed and installed so that a single short circuit caused by a combination of grounds ...