Comparison Yealink CP925 vs Yealink SIP-T54W

The type defines the overall layout and application of the IP phone.

— Wired telephone. Most models of this type are devices in the form of classic landline telephones, a base and a handset connected to it with a wire. At the same time, we note that the base can also be connected to the network wirelessly, using Wi-Fi(see "Interfaces"). Another kind of wired models are original devices in the form of a handset, which must be connected to another device via USB to work.

— Cordless phone. This category includes all IP phones that have a cordless handset in their design. There are two main types of such devices. The first is similar to cordless telephones: the kit includes a base that connects to the network and a handset that only works through the base. The second one is more like mobile phones: there is no base in the design, and the handset connects to the network directly, usually via Wi-Fi. Anyway, wireless models are very convenient due to the ability to move from place to place while talking — the main thing is not to go beyond the range of WiFi. And models of the second type can generally be constantly carried with you, connecting to different WiFi points as needed. The disadvantages of this option are the high cost and the limited operating time of the handset between recharging.

— Conference phone (speakerphone). A specific type of IP phones that does not have a handset at all and works in a hands-free format (see "Features"). At the same time, most models are designed to ensure that several people around the device can talk on the phone at once. Actually, it is precisely for such situations that speakerphones are designed: for example, they are well suited for meeting rooms.

Connection interfaces provided in the design of the phone.

— WAN. Connector for wired connection to global computer networks. The best example of such a network is the Internet, but there are other networks, usually, specialized ones. In IP phones, the WAN port is most often used specifically for connecting to the Internet directly, without the use of routers and other equipment. However, this interface usually uses a standard RJ-45 network port — the same as in the Ethernet interface (see below); however, it is not suitable for working with local networks — WAN and LAN use different communication protocols.

— Ethernet. Wired interface used to connect to local area networks (LANs); colloquially, it is often referred to as “LAN”, it uses a standard RJ-45 connector. Note that in this case, not all types of Ethernet are meant, but only the “classic” version of Fast Ethernet, which supports speeds up to 100 Mbps. It is slower than the Gigabit Ethernet described below, but in most cases this speed is more than enough.

— Gigabit Ethernet. A type of Ethernet connector, characterized by an increased data transfer rate — up to 1 Gbps (hence the name). On the one hand, this connector is considered more advanced. On the other hand, the real need for such speeds arises quite rarely, mainly when transferring large amounts of data (for example, during vi...deo communication). And not all network equipment supports Gigabit Ethernet. Therefore, this interface is relatively rare in IP phones.

— USB. Universal port used to connect external peripherals. In IP phones, this port can be used for Bluetooth adapters, some headsets, external cameras, USB drives (for various purposes), and in the most advanced models, even for keyboards and mice. And some devices with this interface are themselves designed for use as peripherals — these are separate wired models (for more details, see "Type").

— HDMI. Versatile digital video and audio output for high-definition video and audio up to multi-channel. It is relevant primarily for working with video telephony: you can connect a large external screen (monitor, TV or even a wall panel) to the HDMI connector and communicate using this screen, which is much more convenient than using a small built-in phone display. At the same time, the presence of at least one HDMI input is actually mandatory for modern video devices, which provides very extensive possibilities for their connection.

— Card reader. A slot for working with memory cards (most often SD or microSD). In different models, the ways of using such slots may also be different. So, one of the most popular options is to record conversations on a memory card, however, other possibilities may be provided — from purely service ones, such as updating the firmware and loading automatic settings, to playing video files on the phone's own screen and working with Android OS applications (see "Features"). Anyway, the presence of a card reader provides additional features, including exchanging data with other devices. Also note that removable cards are the most convenient way to expand the built-in storage of the device (see below) — in terms of gigabytes of volume, they are much cheaper than built-in drives, and you can choose the size of the card at your discretion.

— WiFi. A wireless interface used to build computer networks, access the Internet through such networks or wireless access points, and more recently, direct connections between various devices. The main advantage of this interface over Ethernet is the absence of wires, which facilitates the installation and movement of stationary equipment, and also allows you to create portable wireless IP phones that work like mobile phones (for more details, see "Type"). Among the shortcomings, it is worth noting a slightly lower reliability and practical communication speed. And a direct WiFi connection can be used, for example, to connect with a smartphone to synchronize contacts and call logs.

— Bluetooth. A wireless technology designed to connect devices directly to one another. The possibilities of such communication in different models of IP phones may be different — it all depends on the set of Bluetooth protocols provided by the manufacturer. The most popular options are connecting wireless headsets and direct data exchange with a smartphone, tablet, etc. (file transfer, contacts synchronization, etc.). The Bluetooth range is about 10m.

— Jack for the headset. A port for connecting a wired headset; it can be either a standard socket like a 3.5 mm mini-jack or a proprietary port. Anyway, wired headsets allow the speaker to keep their hands free — for example, for taking notes — without turning on the speakerphone and without resorting to other tricks like holding the handset with their shoulder. However wired headsets are not as convenient as wireless ones with Bluetooth connection (see above); on the other hand, they have unlimited run time and are cheaper.

— Video camera. The presence of built-in video camera in the design of the IP-phone. This feature allows not only voice, but also video communication — of course, if the interlocutor's equipment also supports this communication format. And some models may provide the use of the camera for its traditional purpose — for photo and video shooting.

— Skype support. Support of the popular Skype messenger by the IP phone. Skype features include not only voice, but also video communication, text messaging, as well as calls to numbers of both landline and mobile users. At the same time, this messenger uses its own communication protocols that are incompatible with popular VoIP protocols (see above). Therefore, communication with another IP phone via Skype is possible only if the other phone also supports Skype.

— Android OS. The presence of the Android operating system on the phone. A key feature of such software is the ability to install various additional applications that may not be related to the original purpose of the device at all (for example, games). Thus, the presence of Android in an IP phone, in fact, turns it into a smartphone and allows you to significantly expand the original features of the device. Note that this feature, usually, requires a touch screen.

— Answering machine. The presence of an answe...ring machine in the design of the IP-telephone. This feature assumes at least support for the classic features of an answering machine — playing a greeting message and recording a voice message from the caller. In addition, extra features may be provided — for example, remote listening to messages when entering a password.

— Caller ID. The presence of caller identification feature in the IP-phone. The purpose of this feature is obvious from the name: it allows the user to see the number from which he is being called.

— Conference call. The presence of the conference feature in the phone allows you to use the device for organizing conversations simultaneously between several people. Thus, during a group conversation, the personal presence of each participant is not required — he can be connected to the conference remotely. At the same time, additional features may be provided — for example, switching to a private conversation with one of the participants. Note that the phones of the conference participants may not support conference calls — the main thing is that it is available on the organizer's phone.

— Speakerphone (speakerphone). Support of hands-free mode. In this case, the voice of the person at the other end of the line is broadcast through an external speaker, and your voice is perceived by the microphone built into the phone. This not only makes it possible to talk without holding the handset in hand, but also allows several people to participate in the conversation at the same time — the main thing is that they are close enough to the device. This feature is found quite often in modern IP phones. In conference phones (see "Type") it is generally a regular (and, usually, the only) mode of operation.

— Support of SMS messages. Ability to work with SMS — short text messages, familiar to most users on mobile phones. Thanks to this feature, you can receive and send SMS messages in the same way as it is done from a regular mobile phone (of course, if such features are supported by the network).

— Echo cancellation. The presence of an echo cancellation feature in the design of the IP phone. The features of modern communication are such that in some cases an echo may occur during a conversation — when the user, with a slight delay, hears his own voice in the speaker of the device. This is very inconvenient, so a fairly large number of modern IP devices are equipped with echo cancellation systems.

— Detection of voice activity. The presence of a system that responds to the user's voice. Due to the operation of this system, the signal transmitted by the telephone is divided into two separate modes — "speech" and "pause"; during pauses, the data transfer speed is reduced and their volume is significantly reduced. This helps to save traffic, as well as make optimal use of the communication channel, without "clogging" it with unnecessary data when there is silence on the line. The disadvantage of such systems is the occurrence of unpleasant "deaf" pauses, creating the effect of breaking the connection; however, they can be compensated by generation of comfort noise (see below).

— Generation of comfortable noise. The presence of a system that generates a quiet constant noise on the line with a timbre that is pleasant to the human ear. This noise does not interfere with conversations and is practically inaudible during them, but it is clearly visible during pauses. Actually, filling these gaps is the main task of this feature: complete silence on the line can create the feeling that the connection is broken, and in the presence of noise, this feeling does not occur.

— Web interface. Support of web interface. This feature allows you to configure the device settings through a regular computer web browser without installing any additional software and without “digging” into the phone itself: just open the service page in the browser at a specific address and all phone settings will be in front of the user. The advantages of the web interface are, firstly, accessibility from any PC or even a smartphone/tablet connected to the local network, and with appropriate settings, via the Internet; secondly, the abundance of settings and the ease of working with them.

— PoE support. Support of PoE — Power over Ethernet technology. This feature allows you to supply power to the device directly via an Ethernet network cable (see "Interfaces"), through the same interface that is used to connect to a computer network. This eliminates the need for a separate electrical connection. Note that in order to use this feature, it must be supported not only by the device itself, but also by the network device (switch or router) to which it is connected.

— NAT/NAPT support. This technology is used to convert internal IP addresses of data packets to external ones and vice versa, thus ensuring that each computer on the local network is connected to the Internet. Support for NAT/NAPT in an IP phone indicates that the device supports certain router features and can be used as an external gateway for a local network (more precisely, subnets — WAN ports are rare even in such devices).

— OpenVPN. VPN stands for "Virtual Private Network". The idea of such a network is that all computers connected to it (including via the Internet) interact as if they are inside the same "local area". This allows you to create private networks, regardless of whether all the necessary terminals are in one physical LAN or not. OpenVPN is one of the most popular (thanks to its free and open source) technologies for creating such networks.

Support of the GAP standard by a wireless type IP phone (see above).

GAP (General Access Protocol) is a technology used in radiotelephones (both conventional and IP). Its main purpose is to make handsets and bases from different manufacturers compatible: GAP supported by the handset and base ensures that they can work properly with each other no matter what brand they are from. In this case, one base can be connected to several handsets, and vice versa. However specific features (like controlling the answering machine from the handset) may not be available when working with non-native bases or handsets.

The maximum number of handsets that can be connected to one wireless IP phone base (see "Type").

Support of more than one handset allows you to organize several parallel handsets on one base — for example, for a large room where it is easier to keep several handsets in different places than to constantly run to the phone to answer a call. In addition, such devices may provide the possibility of a direct connection between the handsets.

The largest number of VoIP accounts that can be stored in the phone.

The VoIP account determines through which server (and, accordingly, through which provider) the phone will work. Support for multiple VoIP accounts allows you to switch between them if you wish, using the one that is most convenient at the moment. For example, you can keep one number for calls within the country and use the second, with more favorable international rates, for calls abroad.

The presence of a touch screen in the design of the IP phone.

Such a screen can be placed both on the handset and on the base (see above). At the same time, regardless of placement, it provides advanced control options: you can operate the device by touching the image on the screen with your finger, just like in a smartphone or tablet. Such control is considered very versatile and intuitive, but touch screens are quite expensive — not only because of the sensor itself, but also because such a screen must be quite large and, preferably, in colour.

Possibility of mounting an IP phone (the whole device or a wired base, depending on the type) on the wall. This mounting option can be very useful in cases where you need to save space on the table, or when there is no surface suitable for placing the phone nearby.