Vincent, the night guard in a factory, has a interphone frequency of 409.9MHz, which was different from the rest of the team, and each of them cannot hear each other clearly. His booth was on the other side of the factory, and he listened to the night station on the interphone everyday during the night time.

夜間保安 Vincent 的保安亭在工廠的對岸，他的對講機頻率是409.9MHz，和其他人相差0.1MHz。他們聽不清彼此的聲音。