EcimDerivedString with the following pattern restriction: (2[0-9][0-9]|[3-7][0-9][0-9])\.[0-9]{1,3}
It follows the format of "MCC.MNC". The MCC/MNC tuple uniquely identifies a mobile phone operator, with Mobile Country Code (MCC) according to ITU E.212. MCC 3 digits (200-799), MNC 1-3 digits.