Publicly Available Telephone Services (PATS) means a service available to the public for originating and receiving national and international calls and access to emergency services through a telephone number or numbers in a national or international telephone numbering plan, and may, where relevant, also include one or more of the following:
A plain old telephone service has high reliability and is unlikely to be affected by local power outages. More modern systems require battery back-up to guard against local power outages. The United Kingdom telephone regulator, Ofcom, has published a guidance note for telephone service providers: "Protecting access to emergency organisations when there is a power cut at the customer’s premises".[2]