What is Steering Gear regulation for tankers as per SOLAS?

As per SOLAS, Regulation 29

1. In every tanker, chemical tanker or gas carrier of 10,000 gross tonnage And upwards and in every other ship of 70,000 gross tonnage and upwards, The main steering gear shall comprise two or more identical power units Complying with the provisions.
2. Every tanker, chemical tanker or gas carrier of 10,000 gross tonnage and up words shall, subject to para. 17, comply with the following,
   • The main steering gear shall be so arranged that in the event of Loss of steering capability due to a single failure in any part of one Of the power actuating systems of the main steering gear, Excluding the tiller, quadrant or components serving the same Purpose, or seizure of the rudder actuators, steering capability Shall be regained in not more than 45 seconds  after the loss of one Power actuating system;

The main steering gear shall comprise either: