Technical Reference 
53 
2.7  Reliability 
The Mean Time Between Failures (MTBF) prediction is calculated using a parts count 
method.  The calculation is based on the Telcordia SR-332, Method I Case 1 50% 
electrical stress, 55 ºC ambient. The MTBF prediction is used to estimate repair rates 
and spare parts requirements. The MTBF data is calculated from predicted data at 
55 ºC.  The MTBF for the board is 61,582 hours. 
2.8  Environmental 
Table 26 lists the environmental specifications for the board. 
Table 26.  Environmental Specifications 
Parameter  Specification 
Temperature   
  Non-Operating 
-40 °C to +60 °C 
  Operating 
0 °C to +50 °C  
Shock   
  Unpackaged  50 g trapezoidal waveform 
  Velocity change of 170 inches/second² 
  Packaged  Half sine 2 millisecond 
  Product Weight (pounds)  Free Fall (inches)  Velocity Change (inches/sec²) 
  <20  36  167 
  21-40  30  152 
  41-80  24  136 
  81-100  18  118 
Vibration   
  Unpackaged  5 Hz to 20 Hz:  0.01 g² Hz sloping up to 0.02 g² Hz 
  20 Hz to 500 Hz:  0.02 g² Hz (flat) 
  Packaged  5 Hz to 40 Hz:  0.015 g² Hz (flat) 
  40 Hz to 500 Hz:  0.015 g² Hz sloping down to 0.00015 g² Hz