Siemens Gigaset Premium E370H: Big Buttons, Extra Loud, Crystal Clear Conversations 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 Gigaset E370A main unit with base is available here). Up to 6 handsets can registered to the base of the E370A. Benefits of using multiple handsets include features such as: intercom, call transfer, & conferencing facilities. As this handset is GAP compatible, it can be registered to other Gigaset bases. For details on what features will work when using the E370H with a different model, please refer to the following compatibility guide.