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VoIP Phones

VoIP Phones

VoIP phones are available in a very wide variety of formats enabling users to take a totally new approach to the way telephone communications is used.

A VoIP phone is very different to the standard analogue (POTS) telephone. Rather than sending the voice signal in an analogue format to the exchange, the phone digitises the voice and assembles it as packets which can be sent over an Internet connection.

As a result VoIP phones are far more flexible and they can exist in a variety of formats. VoIP phones can be handset based phones similar to existing analogue phones; they can be computers, they can be smartphones and they can even be an analogue phone with a VoIP adapter. Phones that existing in computers and are effectively a software application are often referred to as softphones.

VoIP phone technology

In view of the fact that VoIP phones can take a wide variety of formats there are many differences in the hardware. However the same basic blocks and functions are required whatever the actual physical format of the phone.

They all take in sound audio and then the output is data in the format of packets using Internet Protocol.

Within the phone there are several elements or entities. Like all phones there must be an audio interface to the user in the form of a microphone and an earphone or speaker. This converts the analogue audio signals to and from an audio vibration to analogue electrical signals.

When looking at the transmission elements, i.e. where the voice is picked up, processed and sent to the remote end of the connection there are several key elements:

  • Microphone / earpiece or earphone The microphone is obviously the start of the journey. Audio vibrations are received and converted into an analogue voltage. The microphone may be part of a telephone handset or it cold be as part of a headset with boom microphone - in some cases it could even be the microphone installed in a laptop, etc. Similarly for incoming audio, the earphone or transducer is the last stage in the process enabling the signals to be heard.
  • Analogue / digital conversion Once the electrical representation of the audio has been generated but he microphone, this is amplified tot he required level and passed into an analogue to digital converter. This creates a series of samples of the audio signal that can be further passed on to sages within the VoIP phone.

    On the return journey from a remote phone, the incoming audio signal is converted from digits to an analogue signal using a digital to analogue converter. It will then be amplified to a suitable level for the output device.

  • Codec The next stage within the VoIP phone is to encode the audio samples in an efficient form. The circuit used for this is called a codec - this stands for coder-decoder. It takes the audio samples, compresses then as required so that they occupy less bandwidth and then encodes the signal into a standard format. Conversely for incoming signals the codec decompresses the digitised audio and reassembles in the required format.
  • Communications processing This area of the VoIP phone involves many aspects from the management of the signalling to the allocation of the IP address and much more. It controls both the transmission and reception of the data.

    One of the key areas of the communications processing area is the management of the IP addresses. This is achieved using the Dynamic Host Configuration Protocol, DHCP. This automatically configures the network and the VoIP parameters.

    In addition to this, there are other protocols that need to be used to enable the delivery of the voice data over an IP network such as the Internet. These can roughly be split into the management of the media over the IP network. Protocols like H.323 and RTP are used for this. Then there are protocols used for the call management like SIP.

    Some providers may use their own proprietary protocols for VoIP phones. One such example is known as Skinny Client Control Protocol, SCCP which is a proprietary Cisco standard for communicating with H.323 VoIP systems. These proprietary protocols must be able to interact with phones using the more standard VoIP protocols so that communication between any VoIP phones is possible.

  • Transmission & reception hardware With all the data in the correct format and with all the protocols in place the signal needs to be sent out over the required medium. Typically this is over an Ethernet connection, but it is also possible to send it via Wi-Fi. Smartphones will use Wi-Fi or even the mobile connection.

    Similarly for data coming in from the other end of the call, this hardware manages the reception of the incoming signal over whatever medium is being used.

VoIP phones can take many forms and this means that there will be some variations in the actual physical implementations in some ways. However whatever the format for the smartphone, it will contain the same basic function that enable voice communications to be sent and received.

Handset based phones

When looking at migrating from an analogue system to a VoIP telephone system, the most obvious solution is to replace like for like in terms of the way the phone system will appear to the users.

The VoIP handsets look very much like their analogue counterparts, except that they are likely to have a few more controls and possibly a small screen, often for displaying phone books, incoming numbers and various other information. Dependent upon the VoIP phone, the screen may have further capabilities.

The connection to the phone is most commonly via Ethernet although some may have a USB connection and others can even connect via Wi-Fi.

The Ethernet VoIP phones may be powered from an external power supply, whereas others can use a system called Power over Ethernet, where the Ethernet hub or router provides the power and this is passed along the Ethernet cable. This saves the hassle of additional power supplies and connecting wires.

It is also possible to obtain VoIP phones that have DECT incorporated into them. In this way, only a single connection is required to the Internet or other IP network as the other remotes are connected to the VoIP base station via a wireless DECT connection, and the main handset will have a cordless connection to the base.

Computer based VoIP phones

Many companies require their employees to have access to phones and computers, and therefore it makes sense to incorporate the phone into the computer as a VoIP soft phone.

All that is required in terms of hardware is the headset and its associated microphone. Although it is perfectly possible to use the on-board microphone and loudspeaker in a laptop, desktops may not always have them and additionally when used in an office, not all people will want to hear the conversations.

Software is required on the computer. Programmes like Skype, WhatsApp and Viber, are widely used and also there is a host of others. Some of these are intended for computer to computer conversations and do not involve the use of the traditional PSTN and a phone number. Although applications like Skype started out being used for Skype to Skype calls, increasingly now they are being developed to interact with the public telephone network and they are being developed more for business use. Obviously there is a cost associated calls to landlines although for some calls it may be included in the overall contract for the VoIP service. However, check the terms of the contract for this.

The other advantage of using computer based calls is that not only is it often possible to have video as well as the audio, but it is often possible to accommodate techniques like screen sharing, which can be very useful in business applications.

Some VoIP providers give software packages that allow a large degree of integration with other computer applications and this can ensure that there can be some significant gains in overall productivity from using them.

Smartphones with VoIP

Smartphones provide an ideal basis for a VoIP phone. They already possess a significant level of processing and when a VoIP application is loaded they can easily act as a VoIP phone.

Like the laptop or desktop computer approach, smartphones can provide an excellent basis for using VoIP telephony. As with desktop computers there are many applications like Skype, FaceTime, Viber, Line, WhatsApp, Facebook Messenger, and dozens more that provide VoIP telephony. Some of these apps allow calls to landlines, but there is normally a cost associated with these.

Some VoIP providers offer their own mobile apps to enable a variety of different calling methods, and some provide much cheaper international calling when compared to the traditional analogue phone calling and this can be very useful for keeping in contact with friends and family abroad.

In general there can be considered to be two types of smartphone VoIP application. Those intended only for inter app phone calls, and those that can also make calls to landlines. It is also worth bearing in mind that the capability of many smartphone VoIP apps is not has high as that of the desktop ones, purely because of the size of the smartphone screen and what the intended usage. Even so the capability is available with many apps to be able to divert calls to a smartphone when out of the office, etc. Also the capability of these applications is steadily increasing.

Traditional analogue phones with VoIP

It is possible to use traditional analogue phones on a VoIP network, but an adapter is required. called an ATA, analogue telephone adapter, it converts the analogue voice signals as well as the DTMF dealing tones used into the required format for the VoIP network.

If an analogue phone is required to be connected then the VoIP provider will be able to advise, or alternatively the ATAs can be obtained on the open market.

Analogue telephone adapters for VoIP are not particularly expensive, although it is necessary to make sure it is compatible with the requirements of the system provider.

There are many options for VoIP phones. Each can offer its own advantages. Whilst many of the VoIP phones types will work well, it is best to take some time to consider which option will serve the situation best in the long term. Replacing like for like may give a good short term cost saving, but may not reap all the benefits VoIP can offer for the longer term.

Wireless & Wired Connectivity Topics:
Mobile Communications basics2G GSM3G UMTS4G LTE5GWiFiIEEE 802.15.4DECT cordless phonesNFC- Near Field CommunicationNetworking fundamentalsWhat is the CloudEthernetSerial dataUSBSigFoxLoRaVoIPSDNNFVSD-WAN
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