There are a lot of technical and design features that make passenger lifts as comfortable, convenient and safe as they are, but one quirk of their design that a lot of people have experienced over the years is their effect on mobile phone signals.
Whilst this has historically been merely annoying, the systematic switch-off of the PSTN system which is used in many older emergency call features means that a replacement needs to be sourced as people cannot guarantee the use of a mobile phone whilst in transit.
However, a question that is often asked is why mobile phones struggle to take calls and receive data whilst the lift doors are closed, and the answer can be found in the Faraday shield effect.
A Faraday shield or cage, named after scientist Michael Faraday, is any enclosure made from a continuous covering of metal (or any material which conducts electricity). The difference between the two is that a Faraday cage is made of mesh whilst a Faraday shield is made from solid material.
Many lifts form a perfect Faraday cage effect by creating a complete shield of metal conducting frames and walls, and given that many radiofrequency signals can be blocked using a sheet of aluminium foil, the thick walls of a lift will often block phone signals entirely.
As well as this, radiofrequency signals are absorbed by thicker building materials, and since lifts tend to be built in the centre of a building for reasons of architectural convenience, that also helps to block signals.
Finally, the tunnel effect of the elevator shaft also reduces transmission in the same way that phone calls almost always drop when a train or car goes through a tunnel.
It is sometimes possible to fix this using signal boosting systems, and both telecommunications and lift experts can give some expertise on the design and technological solutions potentially available to minimise this inconvenience.