Galvin, P.Rice, J.2009-11-162009-11-162008International Journal of Technology Management, 2008; 42(4):426-4380267-57301741-5276http://hdl.handle.net/2440/53350The standardisation of interfaces in product architectures helps complementary products develop when network externalities are present. However, standardisation may also weaken a technology developer's competitive position when the product knowledge embedded in standardised interfaces becomes accessible, thereby reducing the barriers to entry. Hence, there is a need to simultaneously protect the knowledge that underpins a firm's competitiveness, but also to define the standards that are open to encourage the development of complementary products. In this paper, we analyse different types and levels of knowledge that underpin a product. We apply this analysis to understanding how Nokia and Ericsson maintained their competitive positions during the Global System for Mobile (GSM)-dominated phase of the industry, even though they were instrumental in developing GSM as an entirely open standard.enJournal article002008231310.1504/IJTM.2008.0193840002586806000062-s2.0-4834909954042237