Two-line phone options are seemingly limitless. Retailers advertise a plethora of phones with multiline capabilities. There are two-line business phones, two-line touch phones and two-line cordless phones. Two-line cell phones are even an option now.
All telephones have a jack where you plug in the phone cord. The phone jack is connected to the wall jack, which connects to the telephone company's wiring. The phone jack is lined with contacts, or conductors, that recognize the wires inside the cord and establish a connection with the line. Whereas the contacts in a two-line phone jack automatically recognize all four wires, and thus both phone lines, the contacts in a single-line phone jack only recognize the first line. So even if you have two phone lines up and running, if you plug the two-line cord into a single-line phone jack, you'll still only receive calls from the first line.
Two-line phones instantly recognize both phone lines and detect which one is ringing. It's possible to use two phone lines without using a two line phone, but you have to either rewire your wall jacks or purchase a two-line splitter. These devices plug into a standard two-line jack and split the line, directing the first line to one jack and the second line to the other jack. With a splitter, you'll just have two single-line phones coming off the same jack. One of the phones will receive calls from line one, and the other will receive calls from line two.
Ultimately, two line phones aren't that different from their single-line counterparts. Take a look inside these double-duty devices on the next page.