Old PBX systems are reliable but are not that flexible. Traditional PBX systems consist of hard lined wires, the phone and the operator. Therefore, the area traveled by these packets of data that contains our messages are limited also to the range and distance covered by your wires.
However, as we approach the modern age, advancements in technology has been made and so with the PBX systems also. The rise of the Voice over Internet Protocol or the VoIP gave rise to flexible and more versatile PBX systems like IP, SIP, Hosted, and Virtual PBX systems.
The advantage of the VoIP over the traditional analog is that VoIP can access the internet and uses it to make free and unlimited calls. A VoIP phone or simple IP phone is technology made for the full use of this VoIP phone system.
This IP phone places and transmits telephone calls on an IP network converting analog signals into digital signals over any IP network instead of the Public Switched Telephone Network (PSTN).
Digital IP-based telephone services use protocol such as Session Initiation Protocol (SIP) and Skinny Client Control Protocol (SCCP). The SIP is a communication protocol for signaling and controlling multimedia communication sessions while the SCCP is a proprietary network terminal control protocol originally developed by Selsius Systems and was acquired by the CISCO Systems in 1998. The SCCP is a lightweight IP based control protocol for session signaling with Cisco Unified Communications Manager.
VoIP phones can come as simple software based softphones or a purpose built hardware device that looks exactly like any other telephone or cordless phone. Some traditional telephones are used as VoIP phones using an analog telephone adapter or ATA.
Some common functionality of these VoIP phones includes the following:
- Caller ID
- Call transfer and call hold
- Dialing using name/ID (differs from speed dial in that no number is stored on the client)
- Locally stored and network-based directories
- Conference and multiparty call
- Call park
- Multiple VOIP accounts. The phone may register with more than one VOIP server/provider.
- Encrypted communications
- Applications like weather report, attendance in school and offices, Live news etc.
- Preserving user name/ number when choosing a different service provider (not widely supported).
Although these VoIP phones have gained popularity over the past few years because of its flexibility and features, but like any other technology that exists, it also has its own limitations. And here are some of its known technological issues:
- Requires Internet access to make call outside the Local Area Network (LAN) supported range unless there is a compatible private branch exchange (PBX) system that is available to handle calls to and from outside the lines.
- VoIP phones and routers depends mainly on electricity unlike the traditional phone system that relies on the PSTN. Although, this limitation can be solved using UPS. The Power over Ethernet simplifies this immensely since power can be injected at any connector or at the router.
- IP networks, particularly residential Internet connections are easily congested. This can cause inferior voice quality or the call can be dropped completely.
- VoIP phones can be subjected to denial-of-service attacks as well as other attacks especially if the device is given a public IP address.
- Due to the latency induced by protocol overhead and other factors they do not work as well on satellite Internet, analog and other high-latency Internet connections.
- Various systems exist to allow one Internet telephone user to talk to another entirely via Internet and without incurring the cost of a PSTN call. Some are based on SIP addresses, some on proprietary protocol such as webcam or Internet chat applications. While it’s not uncommon for two clients of the same IP provider to talk to each other online for free, the various Internet telephony applications often do not talk directly to each other – requiring calls to be gated to PSTN and back at full toll rates.
- Some Internet-to-Internet calling systems use non-numeric names for users, gateway or provider names. Any character which is valid in an e-mail address could be used in a SIP address, for instance, but a VoIP phone with a standard telephone keypad can only dial numbers.