Please silence all phones.

e.g. Please silence all phones before the seminar.

 휴대전화 에티켓(Talking about cell phone etiqette)

▶ Turn off your phone before the movies.

   영화 상영 전에 휴대전화를 꺼주세요.

▶ Don't talk so loud. Everyone can hear you.

큰 소리로 통화하지마. 다 들리잖아