Ten Years of Power Aging of the Same Group of Submarine Cable SemiconductorDevices

In the initial stages of the project, the decision to use germanium transistors in the first Bell System transistorized submarine cable was a rather bold gamble to take advantage of their then superior frequency capability while also attempting to mitigate any reliability inferiority to silicon transistors. When the decision was made, in the time period of 1960-61, silicon transistors were clearly the wave of the future and, although still inferior to germanium transistors in frequency capability, had already indicated their reliability superiority. Nevertheless, the results reported here, together with the results of regular aging and actual service experience thus far, offer rather convincing evidence that the desired reliability objectives are being achieved. The first submarine cable using these transistors, a relatively short cable with 136 repeaters, has been in service over eight years. A transatlantic cable with 363 repeaters has been in service nearly seven years. No semiconductor device failure nor degradation toward failure has yet been observed in any of the systems that have no redundancy and in which the failure of even 987