In the early episodes, Section would put a stick-up microphone/earpiece behind Nikita's earlobe, before leaving for a mission. This allowed her to communicate remotely with the base. As the series progressed, in further seasons, they didn't even try anymore; they couldn't be bothered to make it look credible---perhaps assuming viewers took that for granted---and the whole "sticking the silver circle behind Peta's earlobe" was given up. Then the production took their audiences for granted. The actress would just speak her lines as Nikita, while the visuals showed she had absolutely nothing behind her ears. The same for other remotely-speaking characters on a mission. Audiences were apparently expected to suspend disbelief, whenever Nikita was then whispering sans microphone/earpiece while out---often in a loud location such as a nightclub or party, which made no sense whatsoever---and her words were expected to be somehow magically relayed to Berkoff or Michael.