BT 4600 Additional handset: A user-friendly, big button additional DECT handset Please note that this is an additional handset & charging cradle to be purchased for use with an existing system. This handset cannot be plugged into a telephone line, & will not work without a base station (The BT 4600 main unit with base is available here). Up to 5 handsets can registered to the base of the BT 4600. Benefits of using multiple handsets include features such as: intercom, call transfer, conferencing, & shared phonebook.