As discussed in the previous P100 post, P100 is the most common, open-source DTMF based protocol used for emergency lift phone test calls, that provides defined fault codes that don’t change by manufacturer.

What are test calls and how do they work?

The European Standard EN81-28 specifies that an emergency phone call must call out every 3 days to place a test call to verify it’s in working order, and that test call has to be placed to a receiver software that will log the results.

Most manufacturers of emergency phones have developed receiver software that can receive and record the outcome of the test calls.

The first thing a receiver will check is whether the call was placed – if not, it will register that there is a problem with the hardware or the communication link to the phone (e.g., the telephone line).

If the call does go through correctly, it will then check each step of the call handling protocol that emergency telephones follow:

  • call the receiver
  • telephone identifies itself
  • register any fault codes (usually these will be the status of the battery, the speaker, and/or the microphone)

Each autodialler manufacturer uses its own protocol so the average call centre can end up handling multiple protocols and therefore require multiple receivers. This can be a problem as the record of the calls can then be split amongst several receivers, and in some cases, additional dedicated hardware may be necessary (i.e., a dedicated modem, mini server, etc.) which makes the average install base more expensive and difficult to monitor.

New challenges to P100

The emergency telephone uses the voice channel to broadcast DTMF on order to send information. This works well over copper telephone lines, which were designed for analogue signalling, though there is an expense to the owner of the autodialler as each call is charged as a voice call.

As we move into a fibre line network (aka the Digital Switch) that is built to transmit voice and data, rather than only voice, DTMF audio transmissions will face new challenges as fibre networks may not support DTMF at all!

The most common option installers will choose is to install a GSM so the emergency telephone can work over the mobile network.

However, it’s not as simple as just plugging in any GSM as the following issues of P100 DTMF transmission over a fibre line may still occur:

  • compression of the tones over mobile network: the DTMF tone is compressed to transfer it as data, and there is a risk that when it reaches the other end and is decompressed, it may have been modified; making it unreadable by the receiver
  • clipping of the tone: when converted into data, there may be a loss of the top and bottom of the DTMF signal which changes the frequency, again, making it unreadable

In other words: if you push DTMF signals into a mobile network it may present problems and trying to solve this with any 2G gateway may still present a drop in the performance of the calls.

Luckily not all GSMs were born the same.

The digital solution – signal transmission

Currently, not all lift phones are set up to transmit digital data, but this can be easily solved by adding a Digital Communication Platform (DCP) to the emergency communication chain.

As most European manufacturers support P100 as an option for their emergency phones, the DCP (aside from supporting both the Memco and MK proprietary protocols) can act as an interpreter for any emergency telephone that uses the P100 protocol and will then be able to transmit either analogue audio or digital data (via a SIM card).

To explain the analogue compatibility feature of the DCP based on P100: the DCP intercepts DTMF tones generated by the emergency telephone, reads, and converts them into data. In this way, the smaller, local loop (the connection between phone and GSM), remains analogue whilst the bulk of the communication is transformed into data, increasing its reliability.

DTMF to data conversion is a feature unique to Avire’s DCP. The average GSM doesn’t offer this capability.

The digital solution – monitoring and reporting

An additional benefit of using the DCP is that the 3-day test calls are then recorded in the AVIRE Hub monitoring software and can send real-time alerts and notifications if any part of the process is malfunctioning. The reliability of the DCP means that immediate corrective measures can be taken to ensure passenger safety and compliance is in place.

Any autodialler that supports P100 can report into the Avire Hub meaning that you can monitor all those brands of phones from one centralised platform.

Any third-party device that can send P100 communication can be translated by the DCP

By transferring test information as data, there’s also the added benefit of not consuming voice minutes which offers reduced costs by staying within the data allowance.

Once you have connected the DCP to the emergency lift phone, you will additionally have access to enhanced connectivity so you can remotely monitor other data-based equipment on your lift in real-time.

As an added feature, the DCP can futureproof an emergency lift phone setup as it not only works as a converter of a DTMF signal but can transmit data directly over the mobile network when used with a digital audio unit or DAU (DTMF is not involved in this type of communication), offering the most secure and reliable signal.

In conclusion, to benefit from the best of both analogue and digital, the recommended solution is to integrate a DCP into the emergency lift phone setup:

  • the DCP understands DTMF tones and can convert them into data locally
  • test call monitoring (from any P100 compatible autodialler) can be done in one place via the Avire Hub
  • the bulk of the transmission between the lift installation and Avire Hub is done via data, which is currently the cleanest and safest way to send information

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