Systematic approach to modern corded telephone early commutation failure analysis

Typical early failures of modern corded telephones characterized by their inability to provide correct commutation were analyzed. Specifics of advanced mass consumer communication electronics reliability and failure analysis have been discussed. Complementary theoretical and experimental methods were applied in order to effectively evaluate dialing reliability specifics, allocate defects and reveal their root causes. A regular fault tree analysis procedure has been employed, however its limitation is discussed. Results of the telephony early failure analysis related to open and short circuits of flexible flat ribbon cables and printed circuit boards, dialing button dimensions, mechanical assembly tolerance and soldering, and keypad contamination are presented. Various fault interactions were found to be major contributors to failure aggravation. A major part of observed early dialing failures was related to coarse mechanical and electro-chemical causes rather than to subtle component or material degradation. Recommendations for corrective action were developed