1. (a) The functioning of an interlock to prevent the movement of the car shall not be dependent upon the closing of an electric circuit.

2. (b) Any force or forces used to perform any interlocking function shall be so arranged that their failure to cause the interlocking action will prevent the movement of the car. Interlocks employing springs, gravity or a combination of the two forces, may be used when approved by the Industrial Commissioner if the device is found to be safe, practical and reliable. These forces, however, are not considered desirable if they are arranged so that their failure would create an unsafe condition.

   Note:

   Helical tension springs are considered particularly undesirable.

3. (c) The force or forces used to perform any interlocking function to prevent the movement of the car shall be such that even without lubrication the intended functioning of the interlock shall be completely performed.
4. (d) Interlocks shall be so designed and installed as to prevent, as far as possible, being tampered with or intentionally rendered inoperative (except as noted in § 8-1.57 covering emergency release). (See also §§ 8-1.6, 8-1.58, 8-1.59.)

(See definition § 8-1.1.)