portion of network installation and maintenance to private contractors and joint ventures, such as ABB Communications and STCJV (Siemens Thiess Communications Joint Venture). Telstra also owns and maintains the majority of Australia's public telephones. In 2006, Telstra announced it would remove many of the phones, citing vandalism and the increasing adoption of mobile telephones. Telstra Mobile is Australia's largest mobile telephone service providers, in terms of both subscriptions and coverage. Telstra operates Australia's largest GSM and 3G UMTS (branded as Next G) mobile telephony networks in Australia, as well as holding a 50% stake in the 3GIS Ltd 2100 MHz UMTS network infrastructure, shared with Hutchison (Three). As of September 2007, Telstra had an estimated 9.3M mobile subscribers. Telstra Mobile services are available in post-paid and prepaid payment types, known as Telstra Pre-Paid (formerly communic8 Pre-Paid). Telstra's GSM network was the first digital mobile network in Australia. It was launched in April 1993 on the 900 MHz band as "Telstra MobileNet Digital". The GSM network has carried the majority of Telstra's mobile subscribers for the last 10 years and has seen numerous upgrades. 1800 MHz capacity channels were added to the network in the late 1990s as well as GPRS packet data transmission capabilities. As part of the UMTS Next G deployment, the GSM network was also upgraded to a full EDGE data transmission capability in 2006 providing data transmission capabilities greater than 40 kbit/s on its GSM network. In 1981, Telstra (then Telecom Australia) was the first company to provide mobile telephony services in Australia. The first automated mobile service operated in the major capital cities on 500 MHz using the '007' dialling prefix. This network only provided "car phone" capabilities to subscribers as portable hand-held terminals were not practical at that time. The first cellular system in Australia offering portable hand-held phones was launched by Telstra in 1987 using the AMPS analogue standard on the 800 MHz band. This network at its peak had over 1 million subscribers, but was mandated by the government to be closed down by 2000, partially due to privacy concerns which resulted from the AMPS technology, but also because of arrangements undertaken to secure sufficient interest in the GSM network licenses offered in 1992 to competitors. A license condition placed on Telstra to maintain an equivalent coverage footprint at the time resulted in Telstra deciding to deploy an IS-95 CDMA network in its