MobileConnect Call Connectivity the VTech 17550 allows you to connect up to 2 mobile phones to make and receive mobile calls. This allows calls to be made using either your home line or mobile network from any VTech 17550 handset. MobileConnect Phonebook Transfer you can use the MobileConnect to transfer contacts from your paired mobile phones to your VTech 17550 up to 1000 entries in total. VTech's Power Fail back up system lets you make calls during a mains power interruption with your cordless phone. During a mains power interruption you can supply the power stored in your handset battery to the base unit, so you can make calls even when the power is out.