Replacing elevator phones is the most common application among the many POTS replacement projects. In the United States, for example, there are over one million elevators, many of which require POTS line replacement.

However, replacing elevator phone lines is not always as straightforward as it seems.

In our experience, certain elevator brands are equipped with a 'Line Share Switch'. This can be confusing for those unfamiliar with the elevator model because, within the system, you will see two telephone lines. If these lines are connected incorrectly, calls from the elevator panel will often fail to reach your PBX (UC Cloud), yet you will see the device repeatedly dialling on-site.

You might wonder: Is there a problem with the device's CPC (Calling Party Control)?

Calling Party Control: This is an "off" signal sent by the ATA to tell the elevator phone to hang up.

This unusual dialling behaviour is actually caused by connecting the ATA to the wrong line.

How does REM (Remote Elevator Monitoring)  work?

Here is a common REM system structure.

• Line 1: Telephone line connected to the REM unit, which handles data communication with the lift and receives messages from it.
• Block 1: Lightning surge protection unit, which is also connected to an external telephone line.
• Block 3: 'Line share switch' box.

When a passenger presses the "Help" emergency button inside the cabin, the REM system takes over the phone line and performs two distinct actions:

Data transmission: First, it establishes a high-speed data connection via a built-in modem to transmit error codes, lift location tags and root-cause data to the REM system (line 1 in the diagram).

Voice link: Once the data has been successfully transmitted (or there has been no response), the system drops the data connection and switches to voice mode. It then connects the trapped passenger directly to the emergency help station/security department via the telephone line (line 2 in the figure).

If you want the ATA you are installing to replace the emergency line, so that when the elevator alarm button is pressed it dials a 'live operator' to speak directly with the trapped passenger, you need to connect the ATA's FXS port to line 1 of the 'Line Share Switch', rather than the telephone line connected to the REM unit.

If the ATA is connected to the telephone line corresponding to the REM system instead, the elevator will continuously retry because it cannot connect to the REM unit. From the ATA's perspective, this appears as repeated 'hook-off' events, causing the device to continuously detect on-hook and off-hook events, even when CPC is active.

Dive in with the REM system

The REM system supports multiple communication protocols.

P100 is a widely used communication protocol in elevator monitoring and control systems that utilises DTMF signalling. Vola’s ATA supports multiple DTMF transmission methods, including RFC2833, RFC4733, Inband and SIP Info. Regardless of which format your SIP platform supports, we can provide full compatibility.

Additionally, Vola’s ATA is specifically optimised for inbound DTMF transmission. If you use DTMF for elevator programming, you can do so with confidence, safe in the knowledge that transmission errors will not cause programming failures.

If your REM system transmits a specific type of modem signal (FSK), the Vola ATA can also facilitate this. Vola devices support V.150 modem transmission and, with the help of a POTS Media SBC, can ensure the successful transmission of modem signals over 4G networks or in poor network conditions.

How can Vola help on Elevator Phone Application?

1.The entire Vola product line is optimized for elevator intercom applications, offering configurable CPCs compatible with various elevator intercom models; supporting a standard 48V power supply voltage; support enhanced DTMF for programming.

2.Design for Uninterrupted operation, Vola Hardware support 24 hour standby with battery and Internet failover, fully support ASME A17.1/CSA B44 safety code for elevators.

3.Cloud Based Management, Vola provides series function for remote Configuration/Monitoring/Diagnosis, it not only enhance the efficiency in installation stage, but a huge benefit in long-term operation.