For some time, functional decomposition techniques have been applied t
o describe the architecture of telecommunications transport networks.
A group within the transmission and multiplexing (TM) sector of the Eu
ropean Telecommunications Standards Institute (ETSI) has now applied t
he technique to provide a rigorous means of describing telecommunicati
ons transmission equipment. This paper describes rite application of t
he technique to equipment conforming to the ITU-T Recommendations for
a synchronous digital hierarchy (SDH), and describes the benefits of t
he technique to both equipment manufacturers and network operators.