Computer telephony boards - how to choose best option?

We are talking about PCI and PCI Express boards, which are widely used by small and medium-sized telecom operators, Internet providers, contact centers, as well as system integrators in projects where solution flexibility, low price and good scalability are important.

Computer telephony boards are also called IP telephony boards, as well as FXO / FXS boards and E1 boards (depending on functionality). These cards are inserted into computer motherboard slots - PCI or PCI Express. Analogue (FXS or FXO) or digital (E1) telephone lines are connected to the boards. Instead of the term "board", the term "card" can be used, just as the term "video card" is also used along with "video card". The term "card" may seem more accurate, since IP telephony cards are often assembled from several cards that are interconnected or inserted into one another.

Things to Consider When Choosing the Boards You Want to Use in a Project

In our review, we will touch upon the products of several companies playing in the market of IP-telephony cards in Russia - Sangoma, OpenVox, KTS, Cronyx, AGAT-RT, ATCOM, Digium. Here we discuss the technical parameters, and the summary table below will help you navigate the price ratios and issues of availability of boards in warehouses.

Form factor (size)

Some manufacturers produce some boards in one form factor, some in another. If you do one project a year, then it is unlikely that the manufacturer's commitment to the form factor will determine your choice, and if your business is a few or even dozens of projects a year, then it will be easier for you to work with the supplier who will always supply you with boards of the right form -factor, no matter what phone ports and how many you need.

It rarely happens that you need to install an E1 or FXO/FXS board in any equipment. You probably already calculated specifications server that you will use as a mini-PBX or gateway, and maybe even bought it. It will be a shame if you buy cheaper cards, but they do not fit into a case that is too small. 19" rack servers typically require low-profile boards that are no more than 2U high, and not all manufacturers have them.

PCI or PCI Express?

Motherboards with a PCI bus were produced in several versions with a bus voltage of 3.3 V and 5 V (modern motherboards support only 3.3 V). Many manufacturers make different boards for different options PCI and require the buyer to be careful when buying: a board designed for a different bus voltage will refuse to work with a "non-native" bus for it (and, most likely, it simply cannot be inserted into the connector). Other board manufacturers make them universal, suitable for installation in PCI slots with any power supply, with automatic voltage detection; such boards can work with any PCI variant.

The PCI Express bus, the most common in today's servers, has only one power supply option so far. However, when choosing PCI Express cards, you need to look at the length of the connector: PCI Express cards are available in PCI Express x1, x2, x4, and x8 variants. The higher the multiplier, the longer the connector. The buyer should look at the connector where he is going to insert the card before buying: if the connector on the server motherboard is shorter than the connector on the card you are buying, the card cannot be inserted there and it will not work. Some manufacturers specifically make their boards for the PCI Express x1 slot, since such boards can be installed in any motherboard.

An important point is the availability of the desired board configuration for each of the buses: if a manufacturer produces boards with, say, four E1 ports for all PCI options and for PCI Express, then you have more freedom in choosing equipment for your project: if during the design process you need to change more an expensive new server with a PCI Express bus to a cheaper one workstation with the PCI bus, you don't have to redo the entire project and choose telephony boards with a different number of ports.

Support for Asterisk and other software PBXs

The very first and therefore the most common software mini-PBX is Asterisk. In addition to it, there are several other products that are gradually conquering the market. Among them are open Freeswitch, CallWeaver, Yate and commercial 3CX. Boards from the same manufacturers are equally easy to configure to work with any software, other boards are designed to work with a specific software mini-PBX and have only been tested in operation with it. Sometimes the system integrator simply does not have time to deal with several models of boards, because the project needs to be completed urgently. In such a case, it may be beneficial to buy a more expensive board that you already have customization experience with, rather than choosing different boards for each project.

Number of ports

All telephony cards differ in the maximum number of supported ports, this applies to analog cards with FXS and FXO ports, and digital cards with E1 ports. There are analog boards with support from 1 to 12, 16 and 24 ports and digital boards with support from 1 to 8 E1 ports.

The more ports on one board, the better more profitable purchase: firstly, if you already need a lot of ports, it’s enough to buy just one board, and secondly, if you only need a few ports for now, it will be much cheaper to expand in the future, and you won’t have to buy a new server.

The benefit is especially noticeable when buying boards with E1 ports: only 2 boards with 8 E1 ports each allow you to connect up to 16 E1 streams to one server.

Technical implementation

Based on the experience of the experts interviewed for this article, we would advise you not to worry about these technical details if the project involves operating the equipment at half capacity, and the server in which the telephony cards are installed will not provide anything other than voice and fax transmission.

Boards, especially multiport boards, must be designed to withstand high loads. However, "should" does not mean that all manufacturers design them this way. For example, most manufacturers' multiport boards generate an interrupt every time data arrives at one of the ports, while it is much more efficient not to jerk the processor every time an event occurs on the port, but to generate an interrupt when data has already collected in several ports. At low load, the difference will be small, but if your server is a highly loaded mini-PBX with two or more E1 ports, then the savings can be 10-20% of CPU time.

The presence of such subtle, and even not always reflected in the technical documentation features, such as the interrupt mechanism, the quality of the hardware echo cancellation algorithm, the possibility of hardware recognition of DTMF codes and automatic hardware recognition of transmitted faxes makes the boards more profitable: the central processor can take up the execution of those tasks that no one else will not perform, and purely telephone functions will be transferred to the telephony board.

In the summary table below, you can compare the small technical details of boards from different manufacturers and decide whether it is important for you to free the CPU from purely telephone functions or not.

However, if the server is scheduled for voice mail, IVR, playing music to a waiting subscriber, and especially a gateway to the GSM network, the central processor will definitely be busy anyway, and there is no need to load it additionally. In such a situation, a more advanced telephony card that can take on more functions will be a real salvation.

By the way, when planning the load on the server, as a rule, you should expect that one server will perform purely telephone functions - circuit switching, voice and fax transmission, and a billing database, call logging, call recording, etc. service information will be stored and processed on another computer. For small PBXs with several FXS ports, this is not so important, but for larger configurations it is highly desirable, since voice processing operations are carried out in real time, and no one wants the voice to disappear in the middle of a conversation due to the fact that the server decides to do background DBMS cache recording or search for a file with a record of an old conversation.

echo cancellation

About echo cancellation and the reasons for the appearance of an echo, it is worth writing a separate article, and in short, echo is something that should not be in a telephone conversation. Both terminal devices - telephones, and PBX equipment can be responsible for echo cancellation (on long-distance lines, echo cancellers at PBXs in Russia have been installed since the days of the USSR).

In some cases, it is required that the mini-ATS take over the elimination of the echo. The best available echo cancellation hardware in telephony cards operates at 1024 samples per second, canceling echoes that appear with a delay of up to 128 milliseconds.

The function of echo cancellation can be performed by a telephony board, or maybe by the software mini-PBX itself, for example, Asterisk. When hardware echo cancellation is enabled, software should be disabled, and vice versa. The presence of hardware echo cancellation makes the board more expensive, but unloads the computer. It is recommended to use hardware echo cancellation whenever the number of simultaneous calls exceeds 10-12, and for low-power or high-load computers it should always be used.

The introduction of IP-telephony can be hampered in various organizations precisely because of the poor quality of communication, and the reason for poor quality may be poor load calculation. If the main tasks of voice transmission and echo cancellation are assigned to the telephony card, the quality has a good chance to grow and satisfaction will grow along with it.

DTMF recognition

The chip that performs hardware echo cancellation is often assigned the task of hardware recognition of DTMF codes, which is important for IVR systems, since tone dialing is used to navigate through the voice menu - the same DTMF codes: “press 1 to find out your balance, press 2 to contact the secretary.

Modularity

It is common for many manufacturers of cards with FXS/FXO ports to use modules. Most often, the module supports two FXS ports or two FXO ports, some manufacturers make "hybrid" modules - one FXS port and one FXO port on one module. Modules for Digium cards are sometimes called "mezzanines" (in general, a mezzanine is any additional board inserted into the main one).

The more modules supported by one card, the more convenient: for example, for 12 FXO modules supporting 24 FXO ports, one modern telephony card is enough. Different manufacturers have such boards of different sizes, for example, not all of them install these boards in size in 1U and 2U servers. Before buying, you should study the manufacturer's website, find out the exact size of the board, and measure the space inside your computer. If the motherboard is poorly laid out, inserting a long board can be prevented by memory inserted perpendicular to the PCI Express slots.

Some manufacturers make telephony boards that support up to 24 FXO or FXS ports, but at the cost of side-mounted add-on boards rather than the fact that the main board is long. Such short and wide builds can help if the server case is not roomy enough.

Modules of some manufacturers are suitable only for some models in the product line, modules of others - for all models. FXO/FXS modules from different manufacturers are incompatible with each other (exception - OpenVox and Digium).

Drivers

Some card manufacturers ensure their compatibility only with Asterisk on any platform, some - only for software for Linux. The most experienced manufacturers provide drivers and other useful software for all operating systems.

Publicity to the community

Any technique requires careful handling: you need to carefully read the instructions, install the appropriate software and configure it as required by the specific case. Not everyone has enough experience, patience and qualifications to do it all right the first time. Therefore, on the forums of IP-telephony specialists, there is no end to newcomers asking more and more new questions.

If you are using little-known or unpopular solutions, then you should not expect advice from the guru: at best, you will be advised to replace the equipment with something more studied by the community. This does not mean that this advice should be blindly followed, because both the manufacturer and the distributor of equipment new to the market can help sort out the problem. Sometimes this may require knowledge of English - if the board manufacturer is located in China, the USA or Canada. Google Translate and Multitran will definitely help. You should not be shy to ask questions, just like buying inappropriate equipment just because of its fame.

Modern equipment changes quickly, only the company's approach to development remains constant. If a company started by copying someone else's designs five years ago, in most cases it will take quite a lot of years to develop a quality stand-alone product line. Remember: Toyota started producing American-style cars in the 30s of the XX century, and achieved real success only in the 80s ... Some companies that started their century like this (for example, AvtoVAZ) never became manufacturers of modern high-quality cars, despite enormous resources. Therefore, you need to be careful when buying products of domestic and Chinese manufacturers that copy the circuitry and ideas of market pioneers: their prices are lower than those of North American competitors, but the quality of products and technical support can cause criticism.

Distributors in Russia

Digium - Mototelecom, PBX Design, IT Connection
Sangoma-Halokwadrat
OpenVox - All4Net

Board manufacturers in Russia

KTS-VoipTech
Cronyx - CronyxAlder - Agat-RT

pivot table

* Not without reason, popular rumor has always considered the distributor of Digium boards to be the company "ATS Design", which owns the site pbxware.ru and which is closely connected with a number of other sites that have long been known and popular among IP telephonists, including asteriskforum.ru. On the Digium website, Mototelecom is listed as the only official distributor in Russia. ATC Design is listed there as a reseller. In St. Petersburg, Digium boards are sold by IT-Connection, which also positions itself as an official distributor, although the Digium website does not confirm this status. All these companies have warehouses in Russia, but you should check with the respective companies whether it is possible to guarantee the presence of the cards you need in stock.

OpenVox boards are fairly accurate clones of Digium at a lower price, but they are inferior to them in two aspects: firstly, OpenVox makes a clone of the Digium board not immediately after the release of the new model, but several months later, and secondly, there are still some technical differences .

For example, in a relatively recent study (April 11, 2010) that was conducted in Israel (a detailed report on it), it was found that OpenVox boards sometimes lose IRQ interrupts, which leads to dropping parts of words in a conversation, while Digium boards work stably .

The same study noted that under high load, the OpenVox board with one E1 port lost up to 7% of calls, and when processing several calls at the same time, the processor load from OpenVox significantly exceeds the load on the system in which the board from Digium is installed.

In general, it has been noticed that cheaper boards hold the load weaker.

The production of telephony boards is not the main business of KTS, which is probably why I have heard complaints on the Internet and in personal communication about poor technical support and the fact that the probability of buying a non-working or poorly working board is quite high.

Alder boards are usually produced in a standard version, but they can also be ordered in a special version, then up to 64 FXS / FXO ports or up to 8 E1 ports can be placed on one board. The number and price of boards in such an order should be discussed with the manufacturer individually.

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HOW TO CHOOSE THE BEST FAMILY BUDGET?
First of all, you need to agree on what your family budget will be. Depending on the characteristics of the family, you can choose one of three options.

1.COMMON BOILER
With this method of budgeting, the spouses pool absolutely all their income and jointly decide how to spend the money. This option is usually chosen by friendly couples whose relationships have been tested by time. This model of budgeting is often preferred by young families with low incomes, almost entirely spent on current expenses.

ADVANTAGES OF THE "COMMON POOL": All expenses are transparent for both spouses, there are more opportunities to form a "savings fund" for the long-term needs of the family, for example, for the purchase of housing. In addition, according to the observations of psychologists, conflicts over money are less likely to arise in such families: a joint type of budget helps spouses feel like a single whole, strengthens relationships.

POSSIBLE PROBLEMS: In the absence of personal money, spouses cannot give gifts to each other. In addition, all personal expenses, even the smallest ones, have to be coordinated with each other, and sometimes one of the spouses (usually the one who earns less) is embarrassed to ask for money from the “common pot” for their “little joys”. To solve these problems, you can allocate money to everyone that you can spend without consulting your spouse. It is better if this item of expenditure will be no more than 20% of the total budget - 5-10% for each of the spouses.

2. SHARE
In this case, everyone gives part of their income for family needs, and disposes of the rest at their own discretion. The “total” amount goes to the current expenses of the family (food, payment utilities etc.), from which funds are set aside for holidays and for large purchases. Such a model is suitable, for example, for people who have entered into a second marriage and have obligations to children from their first marriage. Shared participation is also convenient if the spouses spend most of their time apart: if they have different hobbies, different friends, etc. The spouses agree on the principles for the formation of the joint part of the "share" budget. This can be either the same percentage of everyone's income (for example, a husband and wife contribute half of their salary to the family budget, and dispose of the other half at their discretion), or the same amount, regardless of the income of the spouses.

ADVANTAGES OF "SHARED PARTICIPATION": This type of budget can also be convenient in a situation where spouses have conflicts due to different attitudes towards money: one is inclined to save and save money, and the other, on the contrary, spontaneously spend. With a shared budget, both partners will have enough money to use as they see fit: one can put the money in a bank account, and the other can go shopping with it. At the same time, it is possible that the whole family will use the savings of the first and the purchases of the second.

POSSIBLE PROBLEMS: If spouses with significantly different incomes agree to contribute the same amount to the family budget, then the one who earns less may have almost no personal money left. Therefore, it is better to contribute the same amount to the “common fund” if the incomes of the spouses are approximately the same. If incomes are unequal, then perhaps the best solution would be "interest deductions": the one who earns more will invest more in the family "wallet".

3. SEPARATE BUDGET
A separate type of budget assumes that everyone manages their own money - there is no “common boiler” at all. Spouses usually pay current expenses in turn, and they “throw off” for large purchases. This model is preferred by people who are just starting a life together and are not yet sure of the strength of their relationship, or by those who value their “personal space” and freedom, including financial.

ADVANTAGES OF A “SEPARATE BUDGET”: A separate budget is also convenient for a “guest” marriage, when the couple does not live together permanently. Complete financial independence of the spouses and the absence of the need to report to anyone on their expenses.

POSSIBLE PROBLEMS: Often the budget in such families is not planned and the general expenses are covered by the spouse who currently has the money. In this case, the lack of agreement on the payment of common expenses can lead to resentment and conflict. To avoid this, it is best to calculate (at least approximately) the amount that the family spends on their own needs each month, and agree on how much of these expenses each of the spouses will take on. Then, if some “current” purchases are paid by the spouse who had money at that time, the second will know how much he owes, and, if necessary, will reimburse the expenses.
If partners trust each other, a convenient option is to agree that one of the spouses provides daily expenses (for food, utilities, etc.), and money for large purchases is set aside from the income of the second.

3 golden rules:

1. All your financial arrangements and plans will be fulfilled only if someone follows this. So choose a family treasurer. Whether it is a husband or wife, it does not matter: it is better to entrust this mission to the most accurate person who is not prone to spontaneous expenses.

2. Learn to feel free to discuss financial problems with each other. Talk openly to your spouse about your needs, do not be afraid to express your disagreement about certain expenses. Hushing up problems sooner or later results in serious conflicts.

3. Agree to never hide your income and expenses from each other. Transparency of the family budget is the key to the strength of your family.

The price factor when choosing a loader, as well as any other equipment, plays an important, and often paramount role. When choosing a loader, everyone tries to be guided by the principle of minimizing costs. Usually they talk about value for money here. As a quantitative assessment of this ratio, in our opinion, it is most expedient to choose such an estimated parameter as the cost of one hour of operation. It may not always be easy to quantify, but if desired, it can still be determined. But this indicator is good because it includes not only the purchase price, but also the cost of maintenance and repair, energy and fuels, and the resource of the loader. When calculating it, one can assume that the best manufacturers usually they declare a service life of 16-20 thousand hours (i.e. 10-12 years with one-shift operation), although there are models that have worked for 40-45 thousand hours. So far, domestic consumers, most of whom are motorists themselves, prefer forklifts as a more “understandable” technique. Indeed, low operating costs and high environmental friendliness of electric forklifts result in certain limitations (the presence of a charger, a place to charge the battery (battery) with a hood and an appropriate battery specialist), but the calculation of the cost of a motor hour often shows that such forklifts can be more profitable.

The higher the intensity of operation, the more reliable and convenient to use the loader should be. For a three-shift regime, only new imported equipment is certainly suitable, or it is necessary to have an increased fleet of loaders. If you work on a loader for only an hour a day, you can buy a used Ukrainian loader. True, in this case there is always a danger that it can get up, and the relative cheapness of spare parts is more than offset by frequent replacement. Therefore, if you still decide to purchase a used car, we recommend that you take the advice of experts: do not buy a model that has worked for more than 10 thousand hours, in the absence of control by the manufacturer, and even more so in our country.

In conclusion, we briefly summarize all the "pros and cons" of classic forklifts with different drives in table 1.

Loader type	Diesel	Gas	Electric
Advantages	it is convenient when working on the street and short-term stay indoors;	power is higher than that of an electric forklift, although it is inferior to forklifts running on diesel fuel or gasoline;	has a much longer "lifetime" resource compared to a forklift, the service life of which is limited by the motor resource of the internal combustion engine;
	does not require breaks in work to change batteries in multi-shift operation, does not require a charging station and a special room for charging;	does not require special conditions for charging (as in the case of an electric forklift), it is operated like a regular car;	has an extended service interval, requires less Supplies and operating costs, which over time compensates for the initial difference in cost;
	the initial cost is somewhat less than the price of electric machines;	it has lower operating costs (gas is cheaper than gasoline and diesel, it needs maintenance less often);	environmentally friendly technology for environment, personnel and equipment;
	practical with a long "shoulder" of cargo transportation	environmental friendliness is higher than that of diesel models.	practically silent during operation;
			there is no such expensive unit as an internal combustion engine
Disadvantages	poor environmental friendliness of machines: when they are used indoors, despite the catalysts and soot filters used (the use of which equalizes their price with electric forklifts), ambient air is polluted, which adversely affects the health of working personnel;	the lack of a wide network of gas-filling stations hinders the spread of gas-and-gas forklifts.	slightly higher initial cost compared to diesel cars;
		environmental friendliness when using them indoors is lower than that of electric forklifts;	requires a break in operation to replace the battery in a multi-shift operating mode;
	need more frequent routine maintenance than electric forklifts (operating costs increase accordingly); replacement of engine oil, oil and air filters is required;	higher noise level compared to electric machines;	need a special room, charging station, attendants
	due to the low quality of diesel fuel in Ukraine, the engine life of any diesel engine is reduced, although the manufacturers of such equipment use double fuel filters with water separators adapted to local conditions to reduce the harmful effects of this factor	more frequent routine maintenance increases operating costs