... bright and create sound, will stop sound after two “Ding Dong”, and enter into standby status after 1 minute. If answer ... ). If the extension intercom is sounding “Ding Dong” then will not repeat “Ding Dong” again, and the calling intercom will create 15 ... intercom called didn’t sound, it will sound two “Ding Dong”, the calling intercom will sound 15 “Du…”, and simultaneously time ...