Data traffic in transmission networks is specified in the number of connections per unit of time, iIn Call Seconds or Centum Call Seconds( CCS), where the centum stands for one hundred. In other words, in one hundred call seconds.
There is a direct relationship between Call Seconds, the CCS value, Call Hours, and Erlang, also a traffic load unit. One call- second corresponds to one call in one second. 3600 call seconds is equivalent to 36 centum call seconds (CCS) or one call hour. This in turn corresponds to one Erlang or Traffic Unit( TU).