A dedicated call block button enables you easily register to the call block list. During an electric power failure, the power stored in batteries can be supplied to the base unit. This allows you to make a call with handset even when the power is out. You can block any specified number, as well as any head string of 2 to 8 digits matching your specified numbers or numberless calls. Communications between the cordless handset and base unit are encrypted, and the encryption password is periodically changed to maintain a high level of security.