The innovation behind TFL-2: why to invest in a good end-of-line device

LDA - Discover our innovative method of speaker line supervision

The innovation behind TFL-2: why to invest in a good end-of-line device

End-of-line devices are used to ensure that the audio signal is transmitted correctly and without loss to the final stage of the system. For safety-critical installations such as those incorporating voice evacuation systems, having a reliable, high-performance line terminator is vital to ensure their integrity.

Line supervision in safety equipment consists of knowing whether all the elements present on the communication line are operating correctly, in the way they are expected to work.

In the case of public address and voice alarm systems, the integrity of speaker lines can be affected for the following reasons:

  • Earth leakages at any of the points of the speaker line.
  • Possible cuts in the line (open circuits).
  • Short-circuit of some elements in the line itself.

These problems can be detected by the equipment thanks to the end-of-line devices, which justifies their use in this type of project.

For these cases, LDA Audio Tech has developed the TFL-2 end-of-line device, specifically for PA/VA systems that are also certified according to international standard EN-54.

The TFL-2 manufactured by LDA Audio Tech provides an accurate measurement of the impedance of the speaker line and allows you to monitor it all the way to the last speaker without a return cable, even on lightly loaded lines. In addition, the TFL-2 also improves the amplifier supervision, not just the line.

Not all end-of-line devices are equally reliable and do not offer the same performance to ensure the integrity of the installation.

Having a TFL-2 in a public address installation implies a series of advantages that make it stand out from other devices on the market. These are the main ones:

  1. Filtered impedance.
  2. The specific design of the measurement circuit.
  3. Invisible power. Extended speaker capacity per line.
  4. Design protection.
  5. Cost-effective.


TFL-2 Advantages

  1. The filtered impedance offered by the TFL-2 allows less power to be used for monitoring because it only generates current at the desired frequency. The power absorbed by the system is much lower than a resistance.
  2. The measurement circuit is designed for the specific EOL frequency, and we can measure the signal with a low voltage, as the analog and digital processing by DSP is optimized for this purpose. The components are chosen to have the best stability and quality.
  3. The TFL-2 end-of-line device allows more speakers to be put on the same line since the equivalent impedance of the device does not need to be contemplated in the line loads that normally add up in amplifier watts. This is due to the impedance curve complementary to the typical speaker impedance curve.
  4. The TFL-2 design features a full protection enclosure that helps prevent problems in the life cycle of the installation, including electrical and mechanical isolation.
  5. The TFL-2 offers excellent value for money, given how much trouble it can save when installed in public address and voice evacuation systems.

Technical resources that provide a more in-depth look at the features and functionality of the TFL-2 end-of-line device can be found on our Support website: