The majority of Public Switched Telephone Network (PSTN) lines in Australia are operated by Australia's largest Telecommunications Carrier, Telstra. Telstra's local exchanges are mainly Ericsson AXE or Alcatel System-12 equipment.
Australia's second largest Telecommunications Carrier, Optus also operates PSTN lines in some towns and cities. Optus' local telephone lines use Nortel DMS100 exchanges and lines are connected to customers premises using their Hybrid Fibre Coax (HFC) delivery system which also carries their Pay TV service.