Intermittent beeping during phonecalls

[Sunking1011]

Has anyone any idea what this might be? It isn't call waiting as that makes a different type of beeping noise.

[NeoBeum]

Minute timer

[Sunking1011]

So how do you turn it off?

[MarlonUk1]

Does this happen when you are in #safemode

[Sunking1011]

I haven't made a call in safe mode yet. Is there anything in the settings that would cause a beep during calls?

[azzido]

This beeping indicate any notification. It is beeping when you are receiving sms/mms notification during a call, e-mail, alarm or any other notification sent by 3rd party app like aomeone sent you a message via Hangout, what's app, facebook/messenger, or any game notification just came. There is no option so far to turn this off or I am not aware of it.