form xxxx xxxx. Mobile numbers are written in the form of ten digits in length, when dialed within Australia, the 0 must be included, plus 4, which indicates the service required is a mobile number. Mobile numbers are conventionally written 04xx xxx xxx. If a landline or mobile number is written where it may be viewed by an international audience (e.g. in an email signature or on a website) then the number is often written as +61 x xxxx xxxx or +61 4xx xxx xxx respectively. (The "Australian national trunk access code" of 0 is not used for calls originated from locations outside Australia.) Geographic numbers Fixed line telephone numbers in Australia (Within Australia, to access a number in another area it is first necessary to dial the trunk code of 0, followed by the area code and then the specific local number). In major centres, the first four digits specify the CCA (Call Collection Area, also known as an exchange), and the remaining digits specify a number at that exchange, up to 10,000 of which may be connected. Smaller exchanges in more remote areas may mean that no more than 100 numbers could be connected to such exchanges. To access numbers in the same area, it is necessary only to dial the eight digits concerned. To access a number in another area it is first necessary to dial the trunk code of 0, followed by the area code (2, 3, 7 or 8) and then the specific local number. The area codes do not exactly match state/territory boundaries. Notable are the part of New South Wales around Broken Hill (a large part of the state's area but less than 1% of its population), which uses (08) 80xx numbers, and Wodonga, which is in Victoria but is within the New South Wales (02) area code. Similarly New South Wales border towns including Deniliquin and Buronga are within the South East (Victorian) (03) area code. Physical exchanges can be allocated one or more prefixes and modern technology allows sub-sets of these number ranges to be allocated to switching entities physically located at a distance from the exchange in which their controlling terminal is located. (Thus, the concept of what a "telephone exchange" is can become somewhat blurred.) Landlines use an open dialling plan: if the caller's phone shares the same area code as the called phone, the area code may be