Telephone numbers in Singapore, also known as the National Numbering Plan, are regulated by the Info-communications Media Development Authority (IMDA). Due to the small geographical size of Singapore, there are no area or trunk codes; all numbers belong to one numbering area, and thus come in the same 8-digit format. Numbers are categorised based on the first digit, thus providing ten possible categories, of which six are currently in use and the remaining four reserved for future usage. History Until 1985, subscribers' telephone numbers in Singapore were five and six digits. Five digits were introduced in 1960s, whereas 5-digit and 6-digit phone numbers were introduced in 1960s as fixed lines grew, but in that year, these changed to seven digits as the introduction of new towns arose (Tampines, Jurong East, Bukit Batok, Yishun and Hougang) and a large number of new numbers were required. Rationalisation was based on geographical locale over the 12 years. On 1 September 1995, the digit '9' was added to the front of mobile and pager numbers, making numbers eight digits, and on 1 March 2002, the digit '6' was added to the front of existing fixed line telephone numbers. The migration to the 8-digit numbering plan was planned to be on 2002, ahead of 2004 deadline. Full telecommunication liberalisation in April 2000 led to rapid growth in the market, resulting in increased demand in numbers. The implementation of 8-digit numbering plan, ensured that there would be a sufficient number resource pool to cater to the expanded telecommunication services. Preparation work started in 1999, as an effective approach had to be worked out for the implementation, with minimum service disruption and inconvenience to customers. The public telecommunication service providers - SingTel and StarHub, implemented the 8-digit numbering plan and ensure smooth service continuity for their customers after the migration. There was a parallel run of 7-digit and 8-digit numbers from 1 March 2002 to 31 March 2002. From 1 April 2002 to 30 June 2002, those calling the 7-digit numbers would hear the number change announced, prompting them to add the digit "6" to the old number, after which the call would be disconnected. After 30 June, callers would hear the announcement that the number was unavailable. In March 2004, in response to the growing mobile phone numbering in Singapore, 8-digit mobile phone numbers starting with the digit "8" were introduced. In 2005, Infocomm Development Authority,