This auction is for two netGuard telephone line isolators from Omega Electronics and one telephone line y-splitter. The line isolators prevent you phone or modem call from being interrupted by someone on the other extension (or extensions if you have three or more of these isolators). You place one isolator on each extension and when you pick up the phone all the other extension with a line isolator are silenced. To allow another extension to listen in, or to switch phones, you "flash hook" (that is hang-up for less than a second). Guaranteed not DOA.