The Vodavi STS 3515-71 has 24 flexible buttons that can be programmed to monitor stations in use, enable one touch speed dial, or to enable system features such as Do Not Disturb, All Call Page, and many more. This phone also has 3 interactive soft keys positioned directly below the 2 x 24 character display that enable quick access to common system features. Compatible with Vodavi STS Series: 3500-00, 3500-01 - STSe Series: 3501-00, 3501-01 - SBX Series: 4000-03 Additional Details ------------------------------ Product description: The Vodavi STS 3515-71 has 24 flexible buttons that can be programmed to monitor stations in use, enable one touch speed dial, or to enable system features such as Do Not Disturb, All Call Page, and many more. This phone also has 3 interactive soft keys positioned directly below the 2 x 24 character display that enable quick access to common system features. Compatible with Vodavi STS Series: 3500-00, 3500-01 - STSe Series: 3501-00, 3501-01 - SBX Series: 4000-03