From 1877 to 1929 the Bell System extended its qualityassurance capabilities, a step that was critical to the company's ability to certify the reliability of its equipment and apparatus and to provide economical service. Learning in this context involved the gradual development of an organizational structure for coordinating and controlling quality-assurance activities at both the staff and line levels and between the corporate elements of the Bell System. Over the course of the initiative, innovative methods of analysis emerged that provided useful new insights into the manufacturing process. The company's adaptation of probability theory, for example, enabled it to launch a comprehensive inspection regime, which became known as “statistical quality control” (SQC). Based on this new approach, Bell succeeded in broadening its manufacturing knowledge, quantifying definitions of quality, reducing costs and risk, thus assuming the more reliable operation of its vast telephone network. Eventually this upgrading of learning led to the formation of a new profession of quality engineering, which found adherents across many industries in the United States and abroad.