Caishan’s work utilizes the ability of sound to spread across space and uses the booth she is in as a connection point for the other five phone booth works. In Zone 1 of London, the area phone code starts with the fixed number "0207". She collected the phone numbers and the maps of where the other five phone booths are based in. When the work is in progress, the phone in the booth will be called by the other five phone booths at different times during the day, and the bell will keep ringing until some passerby picks it up or it’s left to hang up naturally.

The glass on the door of the booth is broken so it forms a pathway linking the interior of the booth with the street outside. The ringing of incoming calls will be heard clearly by people passing by and how they would react to the ringing bell will be recorded by the camera. If they choose to answer the phone, what they hear is the ambient sound in the phone booth at the other end of the phone, that is, the sound of the corresponding work in another space. At different calls, the works at other ends may be a performance, or a still image, and will all be collected by the sound on the phone. If the phone is not picked up, what is recorded would be the sound transmission around the booth during the ringing and passers-by's reception of the sound information of the ringing. The communication between the phone booths uses sound as a medium to transmit another location on the map and events in another scene, crossing the boundaries between urban areas. The information carried by the transmission of sound has no boundaries. The numbers and maps posted in the booth represent the modern way to obtain information—reading of codes, and the ringing of the phone itself as well as a series of reactions and discussions of passers-by are the breaking of the codes.