In condominiums, it is sometimes difficult to set an intercom because there are many cables to pass (one to each apartment from the main board). My idea is to digitize the voice to send it to the selected apartment in packets composed from an head containing the address and data containing he voice. So this system needs only one cable configured as a bus (i.e. RS422). The packets could be encoded or decoded by a low cost DSP. There is no need to compress and voice could be transmited as raw data.