The No. 2 Electronic Switching System has been planned with dependability, maintainability, and operational ease representing a major portion of the total system design concept. The major characteristics that jail under these headings are redundancy, trouble detection, trouble recovery, diagnosis, repair, man‐machine inter j ace, data protection, and operational and administrative procedures for growth and change. All these factors play a large role in both the hardware and software portions of the system design. This article reviews the highlights in each of these areas and describes how they interact in the overall system across both the control complex and peripheral system areas.