L3Harris offers a line of incredibly tough voice radios for firefighters; the XL Extreme. They represent a never-before-seen level of ruggedness: impervious to high temperatures, submersion in liquids, and extreme impacts.
Porticos worked on the XL Extreme Speaker Mic, or ESM, which connects to critical controls and features of the fire radio (also engineered by Porticos). Both devices had high standards for audio quality, ruggedness, and ease of use.
Device Design
To improve usage scenarios, Porticos created an architecture to translate the raw output from a MEMS microphone to a signal that could be packaged for USB streaming. The team then used digital signal processing (DSP) techniques to achieve a specific frequency response, optimizing for audibility in potentially loud environments. This audio conversion subsequently challenged the limits of the available processor resources, so Porticos optimized signal processing tasks to work within the limitations.
The controls on the ESM also needed attention. The device is relatively small and densely packaged, meaning the controls must be sensitive, without being easily damaged. Porticos made extensive use of flexible printed circuits (FPC) to address these requirements. The result simplified assembly, reduced the volume of wires inside the device, and allowed sensitive signals to be shielded without the use of bulky wire.
Because the ESM is powered by a host radio, power consumption must be strictly managed. Porticos developed a sophisticated calculator for the device. It measured power consumption while also estimating further power consumed from usage scenarios, and then projected dynamic component efficiencies.
Testing for Extremes
One of the final tasks was the rigorous stage of testing. As a device critical for safety in extreme circumstances, a validation test plan was developed that included applicable National Fire Protection Association (NFPA) testing, tests devised by Porticos, and tests specified by L3Harris.
One of the most challenging tests requires operation in a 260°C (500°F) environment for five minutes. Some electronic components must be operated above the rated maximum temperature during that test, so the ESM was tested extensively to validate performance and reliability. Porticos generated interface hardware and test applications to simulate a host radio to facilitate that validation effort.
Compliance Success
The XL Extreme Speaker Microphone is the first and only device of its kind to be fully compliant with the National Fire Protection Association (NFPA) test 1802. Porticos engineers achieved all requirements for audio quality, size, ruggedness, and battery life.
This collaboration with the L3Harris team highlights the expertise that Porticos brings to handheld electronics product development. We’re proud to share this project in the Porticos Portflio.
