Telephone numbers in Australia plan (including the "Trunk Access Code"), presented in domestic format. (Geographical region boundaries do not exactly follow State borders.) The current numbering plan would appear to be sufficient to cope with potential increase in demand for services for quite some time to come. The 06 and 09 area codes are completely unused. In addition, each current area code has large number "ranges" unallocated. When dialling from outside Australia, after dialling the appropriate International Access Code it is necessary to dial the Country Code for Australia (61) followed by the nine digit "National 'Significant' Number". (The + symbol is used to
International Standard Text Code available on the International ISTC Agency website. ISTC numbers are hexadecimal, so may be formed from numbers 0-9 and letters A-F. They are made up of four parts: Example: ISTC A02-2009-000004BE-A The ISTC User Manual is the official guide to the use of ISTCs; it is available for download free of charge from the International ISTC Agency's website. International Standard Text Code The International Standard Text Code (ISTC) is a unique identifier for text-based works. The ISO standard was developed by TC 46/SC 9 and published in March 2009 as ISO 21047:2009. The authority responsible for implementing the standard is