Skype Internet phone batteries, Voice over Internet protocol or VOIP handset battery packs, replacement telephone batteries that use the internet to make telephone calls, made over the internet using your IP address either through a service like Skype, Google Talk, Mumble or some SIP ( Session Initiation Protocol) server interface or direct with another user using Peer to Peer. The call is made via your internet connection and data streams from your handset either wired or wirelessly, Wi-Fi through the internet, some of these services are paid for but either way it uses data so if you have a data cap on your internet connection it will use part of that.
There have been a great number of advancements in the services and reliability, also internet connection speeds have increased over the years making Internet VOIP telephone calls a serious contender for quality of service and cost over conventional PSTN telephone system with added services of larger traditional telephone systems like answer phone and fully programmable telephone service attendant that can leave messages, give directions to callers transfer, fax services and many more. It should be remembered that you need a fast a reliable Internet services though to support these extras.
