Step 1: How to detect if a phone line is causing a failure

Telephones have traditionally been manufactured based on the 48V supply and the telephone circuitry often recognises this voltage on the line to confirm that the phone line is in fact there.

When a phone goes dead, there are 2 ways to test if this is due to a problem with the phone line:

  • Try to detect the tone
  • Try to detect the voltage

Traditionally in a copper line, these go hand in hand although in some instances you could lose the tone and still rely on the voltage. As we move into a fibre network, both of these disappear. Voltage is no longer carried, and the phone doesn’t have a tone (same as with mobile phones).

Therefore, even if you add an additional backup supply, it might not make a difference as the phone might still not be able to detect the phone line.

 As this could have a critical effect to the operativity of the phone, it is important to determine whether a phone needs voltage or tone to detect a line. For details of how the specific equipment works, the phone manufacturer should be contacted.

Step 2: What are the recommended, safest options for a lift phone?

Firstly, it’s important to understand what the existing setup is and how can a power supply be added to it. Once that’s decided, it’s important to define how will this power supply be monitored.

Some key considerations when deciding on how to adapt the phone setup are:

  • what will it mean in terms of how the phone will detect a phone line?
  • Is it based on recognising voltage?
  • Does it recognise the phone line?
  • Can it recognise both? Either?

A reliable equipment that can overcome this, such as the Memcom, should be able to do both.

It is also worth considering whether it is worth maintaining a phone line that was solely designed to function with copper lines. This could mean the equipment can’t be upgraded to a digital GSM.

Should the traditional setup be connected to a GSM, it will need the GSM to output a dial tone into the local loop so there is a dial tone that allows the detection of the line. If the phone needs to detect voltage, then the GSM would need to output voltage as well though GSMs won’t typically give out any voltage on their telephone port.

Step 3: Futureproofing lift phones

There is a very real chance that existing installed phones can switch off once the digital switch takes place, or that a new phone is installed but it doesn’t function.

Installers should then decide if they should either check the technical documentation with the supplier to figure out how that equipment detects the phone line and how the battery backup is managed


They can seek to replace it with a digital solution, such as the Digital Communication Platform (DCP) and TOC DAU digital solution that will work with fibre lines.

Other considerations

3-day test calls and monitoring

A very real risk to lift companies is that once the voltage is removed, the 3-day test calls won’t be placed. In the case of companies managing a large number of phones, they might even experience a simultaneous cascade of missed calls because all the installed phones have lost power supply.

This means the lift company will now have to go back to install a power supply via a secondary backup battery and ensure this backup battery is monitored (most likely by themselves).

Problems with the DC connector and backups

Don’t line powered phones have a DC connector? The problem with connecting the phone to the DC is: where do you connect it to? If you connect it to the lift, where is the backup for that? Or in the event of an entrapment, how will it inform the operator that it is running its battery out?

If the battery is setup for the controller, it can last up to 9 hours. Allegedly. But it could also not last that long. If the setup is in an older lift, it most likely won’t even have a battery.

Some might feel compelled to add an off the rack one hour backup power supply to fulfil the EN81-28 requirement, but this backup will not be monitored and it won’t alert the rescue services that the battery has fallen below the minimum one hour of standby that is required.

Mains power failure and the lift phone

For the last 10 years, modern lifts have a big battery installed that, in the case of a mains power cut, will allow the lift to move to a nearby floor and stop with its doors open – this prevents the risk of an entrapment (older lifts will just stop wherever they are in the shaft).

In these cases, when the mains power goes down, it’s worth noting how the emergency telephone will react:

  • Will it remain functional?
  • Will it recognise the phone line?
  • Will it start using up the backup battery?
  • Will there be an alert if the battery goes below the required limit?
  • If it can’t find voltage, does the phone even know it exists?

Line powered telephones will be the first to show the most problems and will also be the most difficult to bring back into a compliant working solution.

Once they lose power, there will be a need to find new power supply and a battery backup. The standard says these have to be monitored – how will this be achieved? Will the telephone even understand a line that doesn’t carry voltage?

IMPORTANT: the ability of the phone to alert if battery has fallen below the minimum compulsory one hour standby is the lift maintenance provider’s responsibility. This sits inside the alarm equipment setup and therefore sits inside the standard requirements.

You can find out more about the AVIRE solutions for emergency lift phones that will ensure compliance and minimise your risk of liability, by visiting our digital switch page or contacting the AVIRE team directly for a free consultation.


Author: Milagros Gamero, EU Marketing Communications Manager at AVIRE

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