One significant issue posed by the change to VoIP is the lack of resilience in the event of a power failure. This factor is especially relevant in rural locations served by overhead power lines, where power outages tend to happen more often and last longer than in urban areas.
In
the existing PSTN, no power supply is needed at the customer’s
premises for an ordinary corded telephone (but a cordless telephone
does need local power). Power for the system is provided at the
telephone exchange where, in the event of mains failure, a battery
provides continuity while a generator starts automatically and can
provide power for an extended period. Exchange equipment for
broadband will continue to function, so standard broadband will work
although the customer would need power for their router and computer.
Faster broadband requires fibre optic cable, which for most
customers at present extends as far as a street cabinet where
equipment converts optical to electrical signals for distribution to
customers on existing copper wires. BT's cabinets have a back-up
battery designed to last four hours,1
after which broadband will fail, but the associated PSTN telephone
line will continue to work. Customers with Fibre to the Premises (FTTP) do not need power at a street cabinet if a passive optical splitter feeds the individual customers; it appears that Openreach are installing passive splitters, and not active splitters that need power to function. However, every FTTP customer has an optical network terminal (ONT) which requires a power supply at the customer's premises.
Under the new system using VoIP, the router necessary for both broadband and telephone needs a local power supply at the customer’s premises. During a power cut the telephone will be inoperative unless the customer has arrangements for back-up power. The regulatory body, Ofcom, have decreed that telecommunication providers must arrange, free of charge, a solution to enable “at risk” customers to make emergency calls during a minimum period one hour following a power cut. It is left to each telecommunication provider to decide on the solution they will adopt. The provider should offer the same arrangements for other customers, but will probably impose a charge for this facility. The solution offered might be a mobile phone with access restricted to the emergency numbers 999 and 112, or a power supply with battery back-up for the router.2
A customer may not become aware of a power cut occurring overnight until several hours later, by which time any one-hour back-up battery will be exhausted and mobile networks, if available, may have failed.
Ofcom recognise “that some individual customers might require protection beyond one hour, for example, because they lived in households with a history of long-duration power outages, and that providers should take steps to ensure those customers were protected.”3 It will be interesting to see what evidence of lengthy power outages will be required by a telecommunication provider before they consider implementing a longer protection period for a customer.
One solution in an emergency is to make use of the mobile phone networks. However, a mobile phone may prove inadequate even when the power outage is of relatively short duration. In densely populated areas it is common for coverage of base stations to overlap, so a localised power cut might not interrupt reception. In a rural area some locations may be within range of only one base station. Some places remain beyond the coverage of any mobile network. One or more base stations serving a location could fail during a power outage over a wide area. Provision of back-up power at base stations varies between network operators. An Ofcom “Connected Nations” report in 2019 revealed that one network operator protects about 5% of its total sites with 4 hours of back-up power; most of its remaining sites have no protection, while an unspecified number of large-coverage sites have 10 minutes. Another operator has no back-up power at the vast majority of its sites. 4 It is thus possible that in some cases a mobile phone network will not be available for a customer to make any calls during a power outage. This crucial topic appears to have been dropped from later Ofcom reviews, so it is not clear what improvement, if any, has been made by mobile phone companies.
In a more recent document reviewing the Telephony Universal Service Obligation, Ofcom say that “We recognise that, in the event of a power cut, the vast majority of people are likely to have access to a mobile phone which they should, in most cases, still be able to use in order to make any necessary calls”.5 This statement indicates either some remarkably prompt work by mobile phone companies installing back-up power, or, at best, naivety on the part of the author of Ofcom’s document.
As to communication between the consumer and their power distributor, Ofcom’s guidance states: “We will continue to liaise with Ofgem and the energy industry, particularly Distribution Network Operators, to ensure they understand the impact of the upcoming changes to how phone services are delivered and can take steps to continue to communicate with their customers effectively during power outages, particularly those that are listed on their Priority Services Registers.”6 Exactly how do Ofcom expect power companies to communicate with customers when telecommunication systems have failed?
It is somewhat optimistic to expect power cuts to be rectified within one hour. Ofgem’s data for the UK for 2016-17 shows that on average 33% of domestic power outages lasted for one hour or longer.7
Ofcom conducted a consultation prior to issuing guidance about the provision of emergency communication in a power cut. Of the 28 respondents, 19 were themselves telecommunication service providers, and one a body representing the telecommunications industry. Another response was confidential and not published. One local authority and one telecare alarm provider responded. The Communications Consumer Panel, the London Fire Brigade, and three members of the public also participated; all five considered that the proposed one-hour protection for emergency calls was inadequate. 8, 9 Discounting the responses from the telecommunications industry, the low number of replies suggests a significant lack of publicity about the consultation.
Understandably, most of the public are unversed in the technicalities of telecommunication networks. There seems to be already a general acceptance that loss of mobile communications is an unavoidable consequence of a power cut, and no questions seem ever to be raised about the inadequacy of back-up power. It is apparent that the widespread adoption of cordless telephones, which also require a local power supply, has induced many people to believe that all telephones will cease to work during a mains power failure. There is no sign of any robust challenge to the false suggestion that customers are no worse off under VoIP than with the existing PSTN.
Minimal publicity has been given by BT about the withdrawal of the PSTN. Such information as has been published emphasises the marginal improvements: improved speech quality and a few extra facilities free of charge which would have normally incurred a fee. BT’s customers are being advised individually shortly before conversion to VoIP. Statements about the inability to make telephone calls during a power cut are somewhat inconspicuous.
One argument submitted by telecommunication providers is that they should not be required to compensate for an unreliable electricity supply, and that electricity distribution operators should improve the resilience of the power network. But local power distribution in rural areas is by overhead lines which are always susceptible to damage, often resulting in a loss of supply to many consumers simultaneously, whereas telecommunication cables nowadays are mostly underground, and a major fault affecting numerous users of the telephone service is a rare occurrence.
References
1. Connected Nations 2019 Ofcom 20 December 2019 at Page 43. A contributor to the BT Community forum in March 2022 has reported that, during an extended power cut, the back-up power to the street cabinet failed after 6 hours (message 9 of the discussion thread).
2. Protecting access to emergency organisations when there is a power cut at the customer’s premises Ofcom 10 October 2018 Paragraphs 3.47 – 3.48
3. Reference 2 above at Paragraph 3.49
4. Reference 1 above at Page 44
5. Review of the telephony universal service obligation Ofcom February 2021 Paragraph 3.124
6. Reference 2 above at Paragraph 3.79
7. Proposed guidance on protecting access to emergency organisations when there is a power cut at the customer’s premises Ofcom 24 May 2018 at Section A1.1 Table 1
8. Guidance: Protecting access to emergency organisations when there is a power cut at the customer’s premises Ofcom 10 October 2018 (Includes details of respondents and links to their submissions)
9. Reference 2 above at Paragraphs 3.67 and 3.76
Further Information
Living without electricity Royal Academy Of Engineering May 2016 at Page 8
Will your landline telephone work during a power cut? Ofcom
