Intercom Central 413 - Three Channels HOME Power-line Intercom System, 3 Wire, White, Three Stations Set READ "Product Knowledge"--2nd picture in the picture gallery BEFORE buying. **** - WARRANTY: 12 months. Stations talk to each other via the electrci wire. Use the setup "Solution" on page 9 of the Manual to find the outlets on that same pice of electrci wire *** NO GFI & ***No Surge protector. GFI will alter how voice travel along the electric wire One Power meter only. All receptacles must have ground. (system is designed for home use only)