VTech CS6909-15 Accessory Cordless Handset, Blue | Requires a VTech CS6919, or CS6929 Series Cordless Phone System to Operate DECT 6.0 digital technology Conference between an outside line and up to 2 cordless handsets Last 10 number redial. Voicemail waiting indicator. Trilingual promptschoose between English, Spanish and French Accessory handset onlyrequires a 6919-x or 6929-x series phone to operate