Digital Intelligibility Failure Boise Fire

[firemedic7526]

The City of Boise Fire Department has reportedly stopped any transition to 700Mhz after a several million dollar investment by Ada County & the city.

Due to intelligibility issues during pass alarm activation and low air warning (scba) the fire department has said that a significant safety issue exists for their employees using "digital" technology over "analog."

[jimvv]

Can you describe the 'pass alarm activation' and 'low air warning (scba)' in detail?

[exkalibur]

They're both very loud and very annoying alarms. The problem is that when they are going off, it drowns out the FF's voice. On analog, at least you can understand what the FF is saying over the noise. However, on digital for whatever reason, it all but eliminates their voice and it's very difficult if not impossible to understand what they are saying.

Thus proving the point again that digital has no place in this particular application. I'm not anti-digital, infact I love the technology and wish everyone were using it...but the fact of the matter is, digital has no place on the fireground.

[firemedic7526]

It has to do with intelligibility on the receiving end. If a firefighter is attempting to communicate while their low air alarm is activated or there is a pass alarm activated (firefighter down) the person/s on the receiving end will not be able to undrstand the message. The "digital" processing of voice and competing noise (pass alarm, low air alarm, etc.) is apparently the issue. The "vocoder" is unable to process (separate) voice vs noise and thus produces garbage as output.

This apparently occures during simplex or duplex operation.

Scary is that fire departments keep purchasing this technology! It will only be a matter of time before an "event" and the fire service will say wtf! How did this happen? We should have been warned!

Boise is not the only agency. Littleton CO., Plainfield IN., Phoenix AZ.. Many more. Some 700 some 800.

[cjrjr507]

Question: Why couldn't they use a low-pass filter somwhere in the comm chain to get rid of the noise ? One that would allow voice to get through but get rid of the alarms. Depending on the frequency of the alarms.

[stateboy]

Originally Posted by cjrjr507

Question: Why couldn't they use a low-pass filter somwhere in the comm chain to get rid of the noise ? One that would allow voice to get through but get rid of the alarms. Depending on the frequency of the alarms.

That is all but impossible in this instance. The FF keys up his XTS5000 on a digital fireground channel and tries to talk while either or both alarms are going off in the immediate background. The radio turns all of this "noise" into digital garbage. It's a function of the digital vocoder in the P25 radio, so how are you going to filter the noise? Write special firmware for the vocoder?

Digital radios should not be used in critical fireground applications. Dispatch? Sure, but not for interior crews.

[cjrjr507]

Oh yeah, that's right. duh! lol