CHICAGO (CBS) — After six years of testing – and spending more than $20 million – the Chicago Fire Department has finally started to go digital.

The switchover from analog to digital radios began Sunday at 8 a.m., with EMS paramedics getting the new radios.

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Motorola got the no-bid contract in 2006, but tests of the digital system showed garbled transmissions and dead zones.

Now, Fire Department spokesman Larry Langford says they’re ready to go digital.

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“The fire department has been testing the system, along with OEMC (the Office of Emergency Management and Communications), and the Fire Department at this time is satisfied with the performance of the system, and we are ready to go live,” Langford said.

Langford says firefighters will start training with the digital radios in June and will switch to digital before the end of the year.

“Every person on the rig will have a radio,” Langford says. That will be a first for the Fire Department – where everyone has a radio.

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A federal report blamed a lack of radios, in part, for the death of two firefighters at a South Side fire in 2010.

The Fire Department disagrees with the conclusion of that report.

“Communication had nothing to do with the onset of that tragedy,” Langford says.

Langford says the department will keep the option to switch back to analog, if necessary.

“Other cities in the past switched into the digital system and found they had problems and could not revert to the analog easily,” Langford said. “We have tested the system thoroughly and we believe the system is up to performance, but because we are always concerned about safety, the analog system will remain available for some time.”

Langford says 500 digital radios are being used by EMS paramedics now.

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About 2,000 radios will go to firefighters, Langford says.