A:AnswerJJ - CS5109 is an expansion handset only, and will not function unless registered to a compatible base system, such as CS5129 and CS5119. The advantage of a multi-handset cordless phone system is that only the base needs to be connected to your telephone line. The additional handsets can be placed in rooms without access to the phone line.
A:AnswerRichard - The CS5119 is expandable up to five cordless handsets. The expansion handset compatible to the unit is the model CS5109. Additional handset/s have to be registered to the main telephone base for you to get a dial tone. Simply place the unregistered handset in the main telephone base (bigger charger) to register. Registration process will take about 60 seconds. When the registration process completes, the handset display shows Registered and you will hear a beep. Hope this helps!
