Introduction

In this paper the author seeks to bring the reader’s attention to an emerging problem. This problem is the requirement for lifts’ emergency phones under EN81:28 to place automatic test calls every 3 days with the assumption that such calls are monitored, acted upon if not received, and that a complete log of such calls can be provided to the lift owner, or a nominated party. A lift should not be in service if the emergency phone is not in service and, therefore, if an automatic test call is not received then the responsible party maintaining the lift must investigate and, it is suggested, shut down the lift in a controlled manner until the emergency phone is confirmed to be operational.

The author suggests that whilst telephone exchanges connecting landlines have been upgraded to properly support Dual Tone MultiFrequency (DTMF) since November 1963, no such rigorous consideration was ever given to the design and operation of mobile networks to support critical test calls, which the lift industry had conveniently automated using DTMF to reduce the burden on human call centre and call monitoring resources.

It should be understood that for voice and Internet Protocol (IP) data calls the mobile networks operate very effectively but little consideration has been given to the transmission of DTMF signalling, which is used for identifying lifts in an emergency call and also registers the automated 3-day test calls to comply with code EN81:28.

The author suggests that there is a growing body of anecdotal evidence based on industry feedback that some proportion of these automated test calls using DTMF, perhaps as high as ten-to-fifteen percent (10-15%) are being lost, scrambled or otherwise failing to transit properly, resulting in a failure of responsible parties to log such calls and respond properly when such calls fail. At a practical level that leaves uncertainty for lift passengers as to whether the emergency phone works correctly and, therefore, as to whether a lift should even be in service.

This issue is, in the opinion of the author, firmly a result of the inherent unsuitability of the mobile networks currently to transmit critical DTMF calls and the lift industry’s determination to keep operating in that manner. Furthermore, the author respectfully suggests that this is matter of sufficient concern that industry bodies such as CIBSE Lift Group and/or the BSI/MHE/4 committee should review the matter and investigate for themselves the scope and scale of the problem, as lift safety, of which the emergency phone forms a core component, should not be ignored by lift industry participants and the standards governing bodies.