Many services running on modern digital telecommunications networks require accurate synchronization for correct operation. For example, if switches do not operate with the same clock rates, then slips will occur and degrade performance. Telecommunication networks rely on the use of highly accurate primary reference clocks which are distributed network wide using synchronization links and synchronization supply units.
Modern telecommunications networks use highly accurate primary master clocks that must meet the international standards requirement for long term frequency accuracy better than 1 part in 1011. To get this performance, atomic clocks or GPS disciplined oscillators are normally used.
Synchronization supply units (SSU) are used to ensure reliable synchronisation distribution. They have a number of key functions: