Cable companies and Internet providers will also provide a bridge device where your phones stay the same and the VoIPing simply happens on the back-end. Just remember that these devices dictate what kinds of features the provider can offer you, so be sure you know what these devices are capable of since there'll likely be more than one model to choose from.
Grasshopper isn’t technically a VoIP and it isn’t technically for residential customers, but it offers basically the same service for a competitive price. Technically speaking, Grasshopper is a cloud-hosted system that works on top of your existing landline or cell service so voice quality doesn’t suffer. While there’s a technical distinction, customers shouldn’t notice the difference. Grasshopper is built for entrepreneurs and small business owners who work from home. The Partner package is suitable for families, as it includes 3 separate contact numbers with up to 6 extensions. 
In 1999, a discrete cosine transform (DCT) audio data compression algorithm called the modified discrete cosine transform (MDCT) was adopted for the Siren codec, used in the G.722.1 wideband audio coding standard.[74][75] The same year, the MDCT was adapted into the LD-MDCT speech coding algorithm, used for the AAC-LD format and intended for significantly improved audio quality in VoIP applications.[76] MDCT has since been widely used in VoIP applications, such as the G.729.1 wideband codec introduced in 2006,[77] Apple's Facetime (using AAC-LD) introduced in 2010,[78] the CELT codec introduced in 2011,[79] the Opus codec introduced in 2012,[80] and WhatsApp's voice calling feature introduced in 2015.[81]
Be aware, however, that there are significant security implications regarding the use of mobile softphones on employee-owned devices. While it's possible for your employees to simply download the appropriate software from their respective app store, your IT department should be involved with allowing access while also confirming that necessary security steps are taken. Also be aware that there are important reasons not to allow soft phone installations on private devices of any type because you may not be able to remove that phone client if the employee leaves the company, and because local laws may impact how much control you have over the use of the device.
VoIP endpoints usually have to wait for completion of transmission of previous packets before new data may be sent. Although it is possible to preempt (abort) a less important packet in mid-transmission, this is not commonly done, especially on high-speed links where transmission times are short even for maximum-sized packets.[18] An alternative to preemption on slower links, such as dialup and digital subscriber line (DSL), is to reduce the maximum transmission time by reducing the maximum transmission unit. But since every packet must contain protocol headers, this increases relative header overhead on every link traversed.[18]
VoIP allows both voice and data communications to be run over a single network, which can significantly reduce infrastructure costs. The prices of extensions on VoIP are lower than for PBX and key systems. VoIP switches may run on commodity hardware, such as personal computers. Rather than closed architectures, these devices rely on standard interfaces.[12] VoIP devices have simple, intuitive user interfaces, so users can often make simple system configuration changes. Dual-mode phones enable users to continue their conversations as they move between an outside cellular service and an internal Wi-Fi network, so that it is no longer necessary to carry both a desktop phone and a cell phone. Maintenance becomes simpler as there are fewer devices to oversee.[12]

Since Verizon is a massive company, customer service ratings are in line with what you’d usually read in the comments section—meaning, people are far more motivated to complain than praise. Navigating Verizon’s bundling plans for businesses may be like a choose-your-own-adventure odyssey, but its support lines are segregated well, with separate contacts for small, medium, and larger businesses. Verizon also offers competitive SLAs (service level agreements) for quality and service and 24/7 support via phone, email, and tickets.

In the case of a private VoIP system, the primary telephony system itself is located within the private infrastructure of the end user organisation. Usually, the system will be deployed on-premises at a site within the direct control of the organisation. This can provide numerous benefits in terms of QoS control (see below), cost scalability, and ensuring privacy and security of communications traffic. However, the responsibility for ensuring that the VoIP system remains performant and resilient is predominantly vested in the end user organisation. This is not the case with a Hosted VoIP solution.
IP Phones and VoIP telephone adapters connect to routers or cable modems which typically depend on the availability of mains electricity or locally generated power.[37] Some VoIP service providers use customer premises equipment (e.g., cablemodems) with battery-backed power supplies to assure uninterrupted service for up to several hours in case of local power failures. Such battery-backed devices typically are designed for use with analog handsets.
Once familiarized with VoIP services,  hone in on what these features can do for you and how to transition to the next level. First and foremost, is cost – a universal concern for anyone. Check the provider’s plans and pricing and be sure they’re the most cost efficient for your calling needs. There is also quality & reliability, portability, customer support, and a satisfaction guarantee; all key factors that may be clinchers or deal-breakers when going through the process.
However, for many businesses there's a need to route calls to the PSTN and other analog phones that might remain in use, too. This may mean a PSTN gateway, or even a hybrid PBX, where there's at least a small telephone switch located on-site. Note that these days, a PBX looks exactly like the other servers in your data center, except with an attached means of handling local and analog phones. Many small businesses, however, are avoiding on-premises PBXes partially due to cost savings and partially because the capabilities offered by all-cloud systems are more than advanced enough for their needs. Some virtual cloud PBXes can handle PSTN connectivity without on-site hardware requirements.

The early developments of packet network designs by Paul Baran and other researchers were motivated by a desire for a higher degree of circuit redundancy and network availability in the face of infrastructure failures than was possible in the circuit-switched networks in telecommunications of the mid-twentieth century. Danny Cohen first demonstrated a form of packet voice in 1973 as part of a flight simulator application, which operated across the early ARPANET.[69][70]
In India, it is legal to use VoIP, but it is illegal to have VoIP gateways inside India.[61] This effectively means that people who have PCs can use them to make a VoIP call to any number, but if the remote side is a normal phone, the gateway that converts the VoIP call to a POTS call is not permitted by law to be inside India. Foreign based VoIP server services are illegal to use in India.[61]
The SIP-T48S IP Phone is a dynamic business communications solution for executives and professionals. This phone offers a large touch screen that makes switching between pages and applications swift, easy and convenient. The SIP-T48S is also with Yealink’s Optima HD Voice technology and wideband codec of Opus for unparalleled audio clarity. Business phone users will think they are sitting in the same room with one another. The phone uses Gigabit Ethernet technology for rapid call handling. Plus, it works in conjunction with Bluetooth USB Dongle and WiFi USB Dongle.
An important disadvantage of the landline is that you cannot easily scale it up or down. This is why many companies with rapidly expanding or contracting business sizes prefer VoIP because it allows enterprise management to easily add, edit or even delete user rights centrally through the control panel. It is not necessary to follow the tedious processes involved if you are using a regular landline. This makes internet phone technology significantly more suitable for large business organizations.
Collective communication is the future of business communication. This type of communication technology enables users to communicate using a variety of data formats. For example, you could text your colleague about something you might have received in an email. Different data formats are combined to ensure that people who are contacted in a way are able to get the message in different ways. VoIP and unified communications go hand in hand.
Each provider will disclose international calling rates on their website and a list of features on their website. We give a standardized list for each provider (with explanations on our VoIP Calling Features page) but providers experiment with different features all the time. Check their website (using a link on their details page) to verify how each  feature works.
At the VoIP level, a phone or gateway may identify itself with a Session Initiation Protocol (SIP) registrar by its account credentials. In such cases, the Internet telephony service provider (ITSP) knows only that a particular user's equipment is active. Service providers often provide emergency response services by agreement with the user who registers a physical location and agrees that emergency services are provided to that address only if an emergency number is called from the IP device.

A high speed Internet connection is required to "carry" your calls so if you have an Internet outage (or your ISP has an outage) then your phone service will not work. Internet services have improved significantly in the last few years and outages tend to be much less common than they use to be. Again, if you have a cell phone then this may not be an issue for you.