Single-Line Cortelco #255444-VBA-27F analog wall phone. This phone is a classic phone that is built to last (5 year warranty). This Cortelco phone comes with a message indicator and a flash button. The flash button allows you to go "off-hook" and perform additional features (transfer, hold, etc) if supported by your PBX, or will you to change lines if connected in an office with regular analog lines.