49 CFR § 236.560
Contact element, mechanical trip type; location with respect to rail
November 18, 2020
Contact element of automatic train stop device of the mechanical trip type shall be maintained at a height above the plane of the tops of the rails, and at a horizontal distance from the gage side of the rail, in accordance with specifications of the carrier.
[49 FR 3387, Jan. 26, 1984]