A major attribute of telecommunications software systems is change. For evo
lving telecom systems, significant expertise is needed to effectively handl
e and capitalize on these changes. This paper discusses some of the key dim
ensions of change that occur during telecom systems software development, t
he areas of expertise that software developers apply in managing these chan
ges, and some of the means by which high-performing project members have ov
ercome the learning curves associated with these systems. We base our resul
ts on data gathered from several Bell Labs multiyear development projects a
nd interviews with experienced staff.