Recommendation B.181)
                                           TRAFFIC INTENSITY UNITY
               The CCITT,
         considering
               (a) that in CCITT texts concerning telephone operations and tariffs and  in
         CCIR texts concerning radiotelephone transmissions  (e.g.  telephone  radio-relay
         systems and the maritime mobile service radiotelephony),  the  quantity  "traffic
         intensity" is used together with the unit in which it is expressed. With progress
         in telecommunications, increasing use will be made of this term and this unit;
               (b) that the  unit  of  carried  traffic  intensity  is  defined  in  CCITT
         Recommendation E.600,
         recommends
               (1) that for telecommunications  purposes,  the  unit  of  carried  traffic
         intensity should be defined as follows:
               Erlang: the unit of carried traffic intensity. The value in erlangs of  the
         intensity of traffic carried by a pool of resources2) over a given period of time
         is equal to the average number  of  resources  simultaneously  busy  during  this
         period;
               (2) that the erlang should be represented by the symbol E.
               Note - The name "erlang" was given to the  traffic  unit  in  1946  by  the
         CCIF, in honour of the Danish mathematician, A. K. Erlang  (1878-1929),  who  was
         the founder of traffic theory in telephony.







































         1)      The text of this Recommendation is analogous to that of Recommendation 665 of  the
         CCIR.
         2)      The term "resource" means any entity used for carrying traffic (circuit, switching
         equipment, subscriber line, etc.).




         Fascicle I.3 - Rec. B.18            PAGE1