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@ATR75 could you try your mobile in Safe Mode & see if it is still there.....normally a 'cog' symbol is some form of settings
http://talk.sonymobile.com/t5/FAQ/How-to-boot-your-phone-into-safe-mode/m-p/348008
Also have a look at this link
http://support.sonymobile.com/global-en/xperiaz5/userguide/Icons-in-the-status-bar/

@ATR75 not a problem...glad it's sorted, must admit i've not come across that icon before :smileysmileythumbsup: