So many building systems are interconnected in ways that are not always appreciated until one part changes in a way that is incompatible with the rest, which is why a general change in telecommunications could potentially make many passenger lifts in the UK unsafe and possibly illegal without alterations.

The reason for this is a consequence of the landline digital switchover, a transition spearheaded by BT that will switch off the existing Public Switched Telephone Network and use Voice over Internet Protocol (VoIP or online calls) for all existing landlines.

This transition has a lot of benefits for the majority of businesses but also has some unintentional side effects for some people, including some of the businesses that would benefit from the upgrades to internet connection speed that come from this work.

The biggest one involves the emergency communications systems that are legally required to be fitted to every lift from 1998 onwards due to the Lifting Operations and Lifting Equipment Regulations 1998 (LOLER).

This legislation requires all lifts to have a line of communication in case of an emergency, given that mobile phone signals are not always strong in a lift.

This device should be easily recognisable, enable two-way communication, require no further action other than activation and have an emergency power supply, and this latter point is where the problem lies.

PSTN and other analogue communications networks carry a low-voltage as part of their use, which allows for basic electrical devices to be powered without having a separate electrical supply.

This is not the case with digital landlines, so a power cut there would leave people trapped in a lift with potentially no way to contact the outside world.

If a building has an older lift, now is the time to check its emergency communication system and potentially replace it with a digital system based on the mobile network, with a battery backup to allow it to run in case of an outage for at least an hour.