Yealink T31Two lines, modern T3 chassis, no PoE needed.

Why the T31 is on the catalog.

The T31 is the version of the T31P (Yealink's most-shipped two-line phone) for sites without PoE. It is the same chassis, same screen, same firmware, same Opus codec support — just without the PoE PSE in the base. Yealink ships the 5V adapter in the box; you plug it into the wall instead of getting power from the ethernet.

Where this lands financially: $10 cheaper than the T31P, but you give up the cable-management win of PoE. For a single home office line, a small retail counter, or a residence, the savings are real and the adapter is not a problem. For a 20-desk office, the math flips — once you are buying half a rack of adapters and routing them around outlets, the T31P's PoE pays for itself in setup time alone.

Where to skip it: any deployment that has even one PoE switch port available. The $10 savings becomes a recurring cable headache. Also skip it if you need a third line or BLF capability — at that point the T33G is the right phone at $50 more, with a color screen and gigabit ethernet thrown in.