Electronic Design

P25 Handhelds Incorporate High-Velocity Human Factors Design

I don’t often write about OEM products. But since I covered the challenges of designing radios for cops and firefighters in the April 30 issue (see “Radio Interoperability—It’s Harder Than It Looks” at www.electronicdesign.com, ED Online 18657), I wanted to follow up because of a new announcement from Motorola.

Vastly oversimplified, the problem facing the radio OEMs and the public safety agencies is that despite everybody’s best intentions, the only real standard we have even now is a voice codec. Beyond that, we have a legacy infrastructure of random frequency allocations in the VHF and UHF spectrum that use various generations of modulation and multiplexing schemes to share that spectrum among federal, state, and local agencies that have different missions and funding channels.

And did I mention that there are politicians and people who wear uniforms involved?

The positive factors include an effort called Project 25 (P25) and the Incident Command System, which are gaining traction. I tried to explain them to some extent in that April article, though it would take a book or two, most likely by authors who didn’t agree with each other, to do the subject justice.

All that aside, Motorola has come up with a really cool handheld radio for first responders that’s both fully interoperable under all P25 modes across all frequency bands (see the figure). It also has some rather well designed human factors engineering built in.

The engineering challenge of making a first-responder handheld fully interoperable across all possible frequencies was initially met only last February by Thales. All by itself, such a handheld is a major design challenge in software-defined radio. The fact that we’re seeing it from Thales and Motorola means that it’s repurposed battlefield technology.

he human engineering in Motorola’s APX family is something else again, or maybe it’s still battlefield technology. It’s called “High Velocity Human Factors,” which is “a paradigm in the human factors sciences that specifically studies human performance in mission critical domains (MCD), such as military combat, law enforcement, fire fighting, etc., when it experiences nonequilibrium,” according to Wikipedia.

“The domain in the human factors standpoint is said to experience nonequilibrium when the situation is perceived by the human agent as being volatile, uncertain, complex and ambiguous,” Wikipedia continues. “This is usually accompanied by stress caused by time pressure and emotional reactions (high stakes, little time) inherent to the event or situation. A major component of HVHF theory is informed by the emotional modulation of cognition in the context of human-systems interaction.”

So, what does that imply for the design of a little handheld radio? Here’s what I remember from my briefing on the features of Motorola’s APX.

First, radios for first responders have a big orange priority-transmit button that’s only used in serious emergencies. When somebody hits that button, everybody’s backlights go orange to tell them some serious traffic is going down.

Second, every radio has a GPS. Unless it’s been told otherwise, it expects that the person carrying it is mobile. If it’s stationary for too long, it alerts the radios of personnel in the immediate vicinity (with a change in backlight color) and the incident commander.

Third, not all tactical communications are oral. These days, there’s lots of routine texting. But when things turn high-velocity, it’s all voice, so Motorola did some interesting things with the control layout.

For example, it moved the fiddly controls to the top, which expands into a “T” shape for a better grip when you’re wearing gloves. It added a big push-to-talk switch, which also is good for gloved hands. And, duplicate mikes and speakers on both sides accommodate righties and lefties.

Finally, it wasn’t all dry-labbed. The APX radios saw a ton of field testing. (Okay, every company does field testing in this business.) But when the firefighters told Motorola that they wanted more dB from the speakers, they got more dB.


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