Lift Report

Since Alexander Graham Bell introduced the telephone at the Great Exhibition in Philadelphia in 1876 the world has fundamentally changed. News, which had previously been transported by coach or ship could now be transmitted in real time. In the course of the first century following the invention of the telephone the networks were extended worldwide and we went from the switchboard operator to modern day tone dialling. However, the basic technology which converted speech into electrical signals and transmitted these, didn’t change for a long time. Change came with network digitalization and the introduction of ISDN in the 90ies. September 1995 saw a digital telephone network covering the entire country. This meant that all voice data was converted into digital information and transmitted via copper wire, glass fibre cable, radiolink-systems and satellite connections before being reconverted to an analogue tone signal at the other end. In the midnineties the onset of the internet boom posed further challenges for the network operators. The data-packages deriving  from internet connections had to be transmitted in parallel to the digitalized voice data. To avoid maintaining two digital systems the entire network was redesigned to carry packages so that today, voice- and video data together with emails and internet connection data can be transferred in the form of small data packages.

The real boom came at the end of the 90ies with the deregulation of the telephone networks, the spread of new transmission technologies such as GSM or ADSL as well as the spread of the internet.

Today, the communication networks are in flux. Digitalisation is advancing and the spread of bandwidth connections is being constantly extended. Not only telephone and internet data is being digitalized but TV, too. A large number of providers, cable-, electricity- and radio network operators offer the end-user a tariff jumble with an unmanageable variety of transmission types. Parallel to the still existent analogue and ISDN connections there are numerous DSL variations as well as the feedback-channel-capable cable connection, even the utility companies are after a slice of the cake and offer to transmit data via the mains. In addition, there are also diverse wireless technologies available. Over and above the various GSM-Standards, UMTS and SkyDSL a wide-spread WiMAX (Worldwide Interoperability for Microwave Access)-network is being set up. This offers bandwidths of up to 108 Mbit/s over distances covering 50 km. Features emphasised during development were high transfer rates and extremely short reaction times. An operating mode with dedicated bandwidths was also integrated. This Quality of Service (QoS) Option is important for telephone and video applications as there is no sudden interruption due to lack of bandwidth. In contrast to other radio technologies, this favours voice data packages ensuring a better voice quality.

This is one important criterium for consideration in the case of transmitting emergency calls with regard to lifts, I will come back to it a little later.

The EN 81-28, issued in November 2003 could not foresee or consider this fastpaced change. For example, while the standard was being developed it was assumed that the communication network would not fail, based on experience with analogue networks over the previous years. Power supply was ensured even during wide-spread power failure, there were no problems with pre-selection or switching problems between VoIP (voice over IP) providers. As most emergency call devices are based on analogue switching technology and use DTMF-tones for electronic identification in the exchange conducting a test call takes a relatively long time and it is not possible to check several devices in parallel. It was for this reason that a test call was required to check the devices and the connection to the emergency call exchange at least once every 72 hours. Although this was a technical and economic compromise it still allowed the person to “survive“. There were no definitions of actions and reaction times to be carried out following a failed test call.

Interpreting EN 81-28 meant something like the following. If a test call has failed and it is not possible to set up a manual connection to the cabin one must assume a person has been trapped for 72 hours which means the reaction times to be adhered to are as in a real emergency call. For a lift compliant with EN 81, a failed test call means the system must shut down as the standard stipulates no lift may run without a properly functioning emergency call device.

The new networks not only open up new frontiers but also bring risks in communicating with lifts. Many networks will be utilised for transferring data to lifts, making it necessary to weigh up the risks and define suitable measures to handle them. All future communication networks will be based on digital transfer technologies which transmit multi-media content. The providers’ marketing strategists advertise bandwidth, flatrates, home- and basic tariffs, but it is seldom that information regarding quality and availability is included. However, this is vital to emergency call systems.

There is tough competition amongst the providers and we see an increasing number of them offering flatrates. The fixed monthly sum covers the cost of transferring speech and data. The currently, slightly higher price for a bandwidth flatrate is compensated as it can be utilised for all systems in the building, for emergency calls as well as remote diagnostics.

This enables the lift operator to be constantly “online” to the lift. If an emergency call exchange and/or a maintenance company were linked up they would immediately notice a system failure and could react quickly. Such a bandwidth supports a videophone connection to the person who is trapped which has the advantage that misuse of the emergency system is easier to detect and it is easier to have a calming effect on the person.

No minimum emergency call voice quality has been defined to date, checks have an extremely individual character. Cost pressure on the providers results in the individual voice bands becoming narrower but with higher compression rates. This leads to distortion, overspill from other connections and gaps in the voice transmission. Some providers cannot ensure availability in the case of widespread power failure. What sense does it make when a standard requires an emergency call device to remain functional for an hour during power failure if the communication network is not sustainable during that period.

Some new business models have appeared against the background of increased competition, the customer can telephone free of charge if he or she is willing to listen to a short advertising slot before continuing the call. Can we even begin to imagine what that would mean to a person trapped in a lift and already under great emotional stress, to have to listen to advertising before placing the call to somewhere at the other end of the world in a voice which is hardly intelligible.

As the lifts are connected to a broadband, digital global internet there is a danger of unauthorised access to the system. It is not only the case of someone eavesdropping on passengers but also the danger of unauthorised parameter manipulation which has to be prevented. The technology is available, the problem lies more in the question of installation and maintenance costs which require qualified personnel. Too little is being done here.

In future, communication will be via the internet. Remote diagnosis and emergency calls are no exceptions. This technical revolution brings about great potential but also harbours risks which are not included in the current standards. New formulations must be found to describe this rapidly developing technology in updated regulations.