Internet telephony providers offers switching to Voice over IP (VoIP) with free calls. Although the calls over VoIP is not really free, since in addition to the monthly base cost for the ADSL connection and the necessary access for the majority of compounds in addition minute rates, but there are cheap call rates and even free VoIP to VoIP. The technical requirements for the transition from fixed line telephony (ISDN / analog) for Internet telephony are now given.
Wiki: IP Telefonie
Requirements for VoIP
May be phoned in different ways on VoIP: more than one free on the Internet available Softphone for PC or Mac, or with SIP phones for IOS and Android devices, with a special IP phone that supports the SIP standard, or by conventional telephone in conjunction with a VoIP adapter (ATA), an appropriate VoIP router or a gateway with VoIP telephone. Be turned on only when the softphone version, the computer in the other cases the rings for the VoIP phone connection, even when the computer used. Besides the phone, a broadband connection for Internet access be available. During a telephone conversation on the Internet is a data volume of about 80 / s to kbps, DSL subscriptions offer beginner so often been a sufficient rate for companies is recommended for a business DSL connection. Manufacturers of network equipment and firewalls now offer switches with VoIP prioritization with QoS will thus ensuring a sufficient reservation of bandwidth for calls (voice latency).
Telephony SIP protocol
When choosing a VoIP provider should be taken to ensure that the selected service, the Session Internet Protocol (SIP). This very open and widespread communication protocol for establishing a communication session is supported by many IP phones and seems to develop a standard protocol for VoIP and ensure unlike proprietary solutions, compatibility with other services. The support of SIP is important to be able to make free calls with other participants over the internet. The SIP telephony also brings location-independent numbers, druch routing numbers can be used at remote locations.
The Aastra 6730i is already there from CHF 111.00 and offers excellent voice quality and convenience features such as caller ID and “Callback on busy” three-way conferencing, 6 SIP accounts, 6 programmable buttons and an integrated XML browser for customized CTI applications.
Many functions with VoIP PBX
Features such as Caller ID – CLIP, Parallel calls, call waiting, conferencing, daytime-and time control, interactive voice recording (IVR), music on hold, Groups (grouping), call center functionality, voicemail transmit voice messages over e-mail notification, Central phonebook, detailed call reporting and overview of costs.
With a SIP phone line saving cost more then the half of the monthly fees then on PSTN phone connection.