GPS modem. Mobile Internet on PDA and laptop

Modern energy accounting systems are increasingly used by GSM networks for data transmission, which finds support from GSM operators, in many respects exhausted the possibility of increasing the subscriber base voice Services. GSM networks are characterized by a developed infrastructure in all regions, high reliability, the possibility of rapid deployment and low cost characteristics.

Analystik-TS LLC, Moscow

All modern GPRS modems are built on the basis of GSM modules of several foreign manufacturers. Easy organization on their access database from a computer to the Internet creates a deceptive impression of the absence of difficulties when using them in industrial systems (availability on a computer Windows Driver and periodic hangs, requiring the intervention of the operator, are not thrown into the eyes). To manage the GSM module can be used:

Functional controller counter, diesel conductor or hub;

Specialized (telecommunication) controller;

The software built into the GSM module and assumes all the tasks of controlling the resistance of communication.

With all types of management, you need to go through the thorny path to turning the GSM module to a full-fledged GPRS modem, providing steady operation in continuous and maintenance-free mode:

Systems running on the table suddenly begin to collect and "hang" when switching to real objects, when changing the operator, - installation in another region or increasing network loading;

It turns out that there is essential efforts to process freelance, ensuring sustainability and safety, testing solutions, accounting for regional characteristics of operators, supporting work with dynamic IP addresses, providing access to the state of the modem and network in the data transfer process, etc.

Of course, there will be organizations that will be able to solve emerging problems, but is it justified by the majority? The complexity of the implementation discussed above lead to the emergence of completed solutions with high functionality. Their cost is definitely a bit higher, but this is the price for a kind of PNP (turned on and run).

We will try to formulate the basic requirements for GPRS modems and as far as possible to justify them.

Basic requirements for GPRS modems

General requirements

Support basic GSM network services: GPRS / EDGE, CSD and SMS.

Interfaces Connecting to Accounting Devices: RS-232C (including "Three-Watering" - RXD, TXD and GND), RS-485, Industrial Ethernet.

Constructive design: Fastening on a DIN rail, built-in source of primary power supply with advanced ranges ~ 140 ... 286 V / 45 ... 55 Hz or \u003d 18 ... 36 V, working temperature range -40 ... + 70 ° C.

GSM antenna: it is necessary to ensure the possibility of connecting external antennawhich can be made of equipment installation zone (for example, from the basement) into the zone of a confident radio.

Automatic establishment of compound

After turning on the power, the modems must automatically activate the setting of the GPRS / EDGE or CSD channel and in some cases ensure the automatic formation of SMS messages when the "events" occurs on additional logical inputs (for example, when the fire and security alarm sensors are triggered).

Ensuring reliability

You must use the following transmission channels backup methods:

At the routing level - between GSM-communication operators (two SIM cards);

At the GSM service level - the transition from GPRS / EDGE to CSD or SMS messages.

In conditions of periodic destruction of the channels without server and client alarm (for example, when rebooting APN servers at the GSM operator), the system hangs play a major role using an independent watchdog timer, built-in transparent ping control of the connection and control of the lack of data. At the same time, it is necessary to provide the ability to optimize the relationship between the "Channel / Traffic (Cost) control depth".

Fig. ASKUPE GPRS Channel Organization Scheme

Security

Authentication at initialization stages, establishing connection and data transmission, including:

To prevent the possibility of using SIM cards, the values \u200b\u200bof their PIN codes must be entered when configuring the modem, which are later stored in the modem memory, are checked at start-up and not available for reading);

APN server access authentication;

Control exchange of identifiers when establishing a TCP connection (between two modem or modem and server);

Control of the caller number when setting the CSD channel.

Using a VPN tunnel between the GSM operator and the dispatch center server.

In some cases, additional data encryption is needed, the use of which is limited.

Comprehensive communication channel solution

The use of modems on a distributed accounting network must be supported by software (telecommunications server), which is installed on the server in the control room and provides:

Simple connection of functional software, for example, via TCP / IP;

Security and stability of the transmission channel (Ping, identifiers, etc.);

Built-in routing, for example for additional ports or technological software.

Optimization of data streams

The built-in data buffering (8 ... 32 KB) allows you to increase the transfer rate by optimizing the interaction between the RS-232C / RS-485 and TCP / IP socket interface, as well as use modems in systems with a "three-wire" interface.

Fig. Scheme of the organization GPRS channel of the system "MOSCAD"

Providing support for various modes of operation

Depending on the features of the solved, the modem task must maintain the modes of operation, combined in two classes.

Monitoring and managing remote objects from the central node with the ability to optimize various criteria, such as maximum functionality, minimal traffic, no ability to use the Internet server side or need to use SMS service on the Internet server side or need to use GPRS / EDGE channels.

The second class of solved tasks is the organization of communication between two points - the interface radio suitorinator (RS-232C or RS-485). In this case, modems must automatically automatically provide a transparent data transmission channel between interfaces.

Providing compatibility

To organize a reliable GPRS / EDGE connection with accounting devices, critical to the rupture of packets accepted by them, for example, using the MODBUS or PROFIBUS fieldbuses using fieldbuses, it is necessary to eliminate the time breaks of the data packets on the reception side. Hope on the possibility of parrying "broken" packages due to repeated polls or work with short packages leads to the emergence of systems operating only on the table from developers.

Operational requirements

Automated remote configuration of modems via CSD or GPRS / EDGE channels without exiting objects, for example: when installing the factory configuration is used, when testing it changes to the system integrator configuration, during operation - to the customer's configuration;

Upgrading the built-in modem software directly on the object, ideally for the GSM network;

Local and remote analysis of the GSM network parameters to configure the antenna position, analyze the surrounding GSM cells, select the telecommunications operator providing the best working conditions at the modem installation point, analyze the reasons for the degradation of communication during operation;

Automatic control of the balance of the SIM card account and an alert in case of declining it to a specified level;

Creation and security remote access to the log files of interaction processes with the GSM network.

Additional features

Of particular interest is to combine the functions of the modem and the instrument of accounting (or its part) in one device to reduce the total cost. Prerequisite for this is the presence of powerful computing resources in modems. Examples of such devices:

Modems with built-in functional software, which provides interaction with accounting devices (for example, autonomous reading and accumulation of measurement results);

Modems with multiple interfaces that provide multiplexing data from multiple interfaces in a common radio channel for independent functioning of several systems.

Service software

Working with GPRS modems should be supported by a set of technological software that provides configuration, testing, remote configuration, monitoring and managing additional interfaces, remote analysis of the GSM network parameters, upgrading the built-in software modem, TCP / IP functions and OPC servers.

conclusions

GPRS modems used in energy metering systems have significant differences from modem used to access the Internet. Requirements for them are constantly increasing. Today, the author is unknown to implement all the requirements discussed above in one modem, which is probably not required if you consider the cost criterion. The article would not be complete without the examples of the use of ANCOM RM / D GPRS modems in energy accounting systems.

Examples of implementation

ASKUPE (automated system of commercial metering consumption of energy resources). Project implemented by OAO MOKEK (Moscow United Energy Company), 2009

The objective of the project is to ensure technical and commercial metering of thermal energy at the facilities of Moscow, serviced by MOEK, and this is 70% of all residential buildings and production facilities of the capital.

Consider the system of remote access to heat supply devices implemented in ASKUPE. Company "KOMKOR" (Brand "Akado-Telecom") builds corporate multiservice Network For OJSC "MOCE", within the framework of which access to heat supply devices according to the Digital Channels of Akado, where they are, and the GSM-operator GPRS channels. The task of providing information security data security is solved using a special MTS service for corporate clients (dedicated APN, local static IP address). System integrators (NGO "Thermalism" and LLC "EUROKOM") are used in ASKUPE Ancom RM / D modem (more than 800 accounting points).

When installing modems, the main problems were associated with the choice of the installation site of the GSM antenna in the basement. The following technique was developed:

All operations discussed below are carried out with the SIM card selected in the GSM operator system;

Search for signals (at least minimum level) - using a cell phone, often it is near windows, outstands or specific places at the walls;

Control zones using an ANCOM RM / D modem and NetMonitor GSM_RM. The signal level, the number and type of visible GSM cells is measured. It is necessary to ensure:

Level more minus 95 (RXLEV: -65 ... -95);

MNC visible cells should match the SIM card operator MNC (with the unavailability of SIM card operator in access to access to emergency services Information about the available hundreds of other operators is issued);

The visibility of more than 3 hundred, one of which is preferably GSM-1800 - there is more free slots in it (BCCHFREQ: GSM-900 from 1 to 124 and GSM-1800 from 512 to 885);

The presence of a high signal level, but 1 ... 2 honeycombs of GSM-900 may in some cases not to provide a stable GPRS connection due to their high load (the IP address is not provided);

GPRS control (provision of an IP address from the network) using a modem (enabled process information information) and GTEM (the presence of GSM communications does not always guarantee the operation of GPRS);

Control of work in the system (regular settings).

The general approach to the GPRS organization is determined:

It is incorrect to try to use antennas with a very long wire (attenuation of 5 M wires RG58 at a frequency of 1800 is 4.5 dB);

In most cases, it is more correct to move the modem into the zone of confident reception, using the RS-485 interface for communication between the modem and heat supply device;

As a result, the use of modems embedded in the heat supply device is often difficult;

Time auto-resistance timeouts need to be selected based on the period of heat supply survey period (including in test mode) and the separation period of unused Socket at the GSM operator;

It is advisable to use an antenna with small attenuation in the cable and a high gain (for example, Ant K996A 900/1800 MHz: amplification, DBI - 5/4; attenuation in the cable 5 m, dB - 1.8 / 2.5).

The system of telemetry of gas metering nodes "MOSCAD" is implemented by LLC "Indasoft", 2007-2009

Commercial Accounting System, providing control over gas consumption modes, monitoring the status of equipment of the accounting assembly and security alarm. Installation and commissioning of the first and second queue are carried out: 1464 objects in 15 regions of the Russian Federation. An essential experience of using GPRS communication in various regions was obtained.

Features of implementation are the ideology of the "active control point": the remote controller independently monitors changes in technological parameters and decides to send data to the top level in accordance with predetermined settings, and does not expect its turn in the cyclic survey of accounting nodes.

Using the MDLC specialized protocol motorola Guarantees the delivery of data to the Regional Gas Manufacturing Manager, remote configuration and programming of all controllers in the system. Through the Internet Gateway of the Regional Gas Company and the Communication Server, the data enroll in the controller top level ACE 3600. The controller "disassembles" the MDLC package, retrieves the data of the gas metering node, processes them, places it in the internal database and initiates the transmission to a data server that provides data to the control system of the regional gas company.

Protection of information from unauthorized access is provided at the MDLC protocol level due to the isolation of the telemetry system modems from the remaining GPRS subscribers of the cellular operator by highlighting them into a separate group with its access point (APN server) and the creation of a VPN-tunnel. Reliability parameters are provided by reserving the GSM communication statement (two SIM cards).

Conclusion

Wireless GPRS modem Ancom RM / D is an important element of any modern distributed system Accounting energy. Providing a reliable communication in the system, GPRS modems allow you to combine hundreds and thousands of remote accounting devices into a single information network. Using ANCOM RM / D GPRS modems in automated systems Accounting allows you to obtain accurate, reliable information about energy consumption, eliminate the influence of the human factor, prevent emergency situations, follow the technical condition of instruments and premises and, as a result, in general, increase the economic effect of applying accounting devices.

I.V. Dianos, Technical Director,

LLC "Analystik-TS", Moscow,

In the last couple of years, there have already been regularly reporting messages about the release of all new and new models of devices relating to a special class of hardware - GPRS modems. What is it?
Maximum short GPRS modems can be characterized as another type of wireless data transfer devices. Their principal difference from other instruments of this group is that they work using one of the options for packet transmission technology implemented in the GSM cellular network networks and the name of General Packet Radio Service, or abbreviated - GPRS. The development of this technology The two largest Russian cellular communications companies - VimpelCom and Mobile TeleSystems - began in 2000, and now the total number of cellular networks in the world that introduced GPRS is already calculated by hundreds. Questions of organization are solved and international roaming For subscribers working in this mode. All major properties and features of the work and parameters of this type wireless modemsThe use of such a technical solution becomes more clear after familiarization with the essence of the GPRS technology itself. On this topic, our magazine has already written about one and a half years ago, so now we will only briefly recall the basic essence.

Why was GPRS was created?
The current stage of development of our industrial society led to the fact that for the successful work of many modern "information production" is not required, so that a person is geographically "tied" to a separate machine, room or even the entire production complex, and only it is necessary that he Just constantly "in touch". Numerous modern means of telecommunications, and first of all mobile, partly allow you to solve this task. But if a person, for example, should participate in the collective processing of large data arrays, then the phone does not really save the position. After all, it is not pleasant for hours to engage in dictation or reconciliation on the phone number of numbers in some reports or reports. Yes, and it is difficult to call such work. Another thing, if this data, literally one click on the key, you can quickly transfer to any required subscriber and just get others. In this case, for successful collaboration, it becomes absolutely no matter where you are: in the office, at home, in the train coupe, in another city or abroad ...
In general, according to analysts, people's needs in mobile transmission Data in the foreseeable future will increase annually at least one and a half times.
Of course, we must not forget that the possibility of transmission of data in cellular communication was implemented almost from the very beginning of the work of such networks, but only in practice this opportunity has long been almost theoretical - to use it, people did not really want - literally units of interest on the total number of subscribers All over the world! And the main reasons here were two: slow and expensive. Indeed, for example, even modern cellular The second generation of GSM standard provides data transmission at a speed of only 9.6 kbps. You can imagine how much this speed is "modern" you can simply remember that modems users on ordinary telephone lines completely abandoned such speeds already more than five years ago. Yes, and the method of communication on the voice channel with a minimal payment made on the online, although it is possible, but very expensive.
Here to eliminate these flaws and GPRS technology was invented. Its goal was to significantly increase the data transfer rate through cellular channels, as well as providing the "permanent connection" mode of subscribers, like this is implemented in local computing networks. But unlike local networks, the working area here turns out to be the entire coverage area used cellular networkAnd taking into account roaming - almost all areas of the Earth, where GSM cellular networks operate. Such coverage today is not available, in fact, no other wireless technologies, with the exception of satellite. This consists of one of the principal advantages of GPRS technology.

Technical Essence of GPRS
First of all, it should be noted that GPRS technology is focused on applying only in the digital cellular cellular networks of the GSM standard implemented based on the temporary access method - Time Division Multiple Access (TDMA). It is the use of the features of TDMA and is obliged to appear GPRS.
Simplified, the essence of the TDMA method is as follows. All the time of operation of one communication radio channel is divided into standard time intervals distributed in turns between several subscribers. As a result, on a radio frequency it turns out to be possible to transfer several conversations at once, or organize several independent data exchange channels. In the GSM standard, the maximum number of such channels is eight.
Such temporary separation of the communication channel between multiple users allows you to increase the number of simultaneously serviced subscribers, but all channels are engaged only in rare moments of peak loads in the cellular network. The rest of the time some of these channels are free. Here on this feature, the idea of \u200b\u200bGPRS technology was founded: in cases where the subscriber needs high-speed information transfer - temporarily "give" free time intervals in this radio channel. Thus, the speed of information transmission can immediately increase several times.
But that's not all. The GSM channel itself can provide a slightly greater information transfer rate if other coding methods are used. Without a noticeable reduction in quality, the data transfer rate can be increased to 14.4 kbps, and potentially - even up to 22.8 kbps. From here, there are high data transfer rates in GPRS: up to 115 kbps, and in the limit - more than 170 kbps. Moreover, it is precisely much of the high speed of communication that it is enough to highlightly allocate increased resources to one of the users for a while, not risking noticeably reduce the chances of other subscribers to reach the network. Indeed, in GPRS mode, for example, getting even quite large email The size with a whole typewritten page can be carried out in just tenths of a second. And if you consider that the latency of radio resources delayed in the GPRS technology should not exceed 1 second, the exchange of small amounts of information between users will occur almost instantly. Such significant changes in the conditions of data exchange using mobile terminals opens up numerous new features.

Functionality
One of the greatest advantages of the GPRS mode is that the subscriber device in pauses between reception and data transfer "does not take line." The mobile network operator simply "remembers" that the user is ready to transmit or receive data, and the radio channel resources are allocated to it only for the exchange of information. In other words, any GPRS devices can be connected in touch continuously (unless, of course, are included and located within the network coverage area) - in the "Permanent Virtual Connection" state. At the same time, the operator has no need to demand from the subscriber of payment of all the time it is connected to the mobile network (in fact, 10 hours a day), but only the intervals of the active work of its terminal or the amount of transmitted and received information.
Great features GPRS technology opens up and before the development of telemetry transmission systems, remote monitoring, security systems, industrial electronics, etc. It is convenient for GPRS technology and for cellular network operators, as it, being upgrades existing networks GSM along the path of their development to third-generation communication systems does not require a fundamental replacement of equipment. True, subscribers, from this point of view, the opposite are in the loss - to use GPRS services, special terminals must be needed supporting this technology.

Custom equipment
Accepted GPRS implementation scenarios provides a phased increase in data transmission rates. This is done, in particular, due to the restrictions imposed by the current subscriber terminals. The fact is that the maximum speed of receiving and transmitting information that the mobile terminal can provide depends on the number of channels (the number of time slots) supported by it and transmission. While all GPRS subscriber terminals are able to maintain from 2 to 4 channels for receiving information and 1 or 2 channels - to transfer. This allows you to get the maximum speed of receiving up to 57.6 kbit / s and transmission - up to 28.8 kbps (real speeds that depend on the loading of the cellular network and defined by the actual presence of time-slot free from voice traffic, in the process of operation can change significantly And in practice be significantly lower). In the future, we should expect the appearance of GPRS terminals supporting greater (up to 7) the number of channels for reception and transmission and capable of providing higher communication speeds. From the standpoint of the functioning algorithm, the standard provides for the existence of GPRS terminals of three different classes:
- class A models should provide simultaneous work in the telephone mode and in GPRS mode;
- Class B terminals also support and voice connections, and batch data transmission, but these modes are not implemented simultaneously - during the data transmission process via GPRS, the subscriber cannot perform and receive voice calls, but the terminal must respond quickly to incoming calls and allow no data loss suspend the session to answer phone call;
- Class with work-oriented in turn in modes - GPRS and telephone.
In fact, all Mobile Phones now produced in the world with GPRS support (and these are more fiddled models) belong to the class B and have means for connecting them to a computer through a special cable or infrared port. And one of the predominant embodiments of class C devices (although classes A and b) can be GPRS modems performed either as a PC card connected to a portable computer or in the form of small-sized GPRS modules focused on using Various equipment - from laptop computers to industrial electronics.

GPRS modems and modules
The number of similar devices currently available now is already several dozen and in the very shortest future it will undoubtedly increase, because their creation today is engaged in very many well-known firms: Ericsson, Motorola, Nokia, Novatel, Ottion, Option International, Pretec Electronics, Real Time Devices, Siemens, Sony, Wavecom, Xircom, etc., who caught the prospects of this direction.
What are the main advantages of applying specialized devices, compared to the use of ordinary mobile phones with GPRS support?
They can be called several at once, but they are determined, first of all, the features of constructive performance, as well as the functionality and parameters of such modules, which determine the areas of their preferential use. For ease of explanation, all these features can be divided into several groups:
- "Wide functionality"This is not just a slogan - many devices of this type are designed to work in several (or even in all!) Ranges of frequencies used by modern GSM networks (EGSM-850 MHz, GSM-900 MHz, DCS-1800 MHz, PCS- 1900 MHz), which allows you to use such modems, practically all over the world. Also, the universality of using such devices is also ensured by the fact that several data transmission technologies are often implemented in them possible in GSM networks: traditional GSM modem (speed 9.6 KBIT / s), batch transmission in GPRS mode and transmitting in switching mode HSCSD technology (High Speed \u200b\u200bCircuit Switched Data), close by methods and parameters to GPRS. In addition, modern GPRS modems, as a rule, support all functions, Provided by the phase of development of the GSM 2+ standard, including SIM Application Toolkit et al. As a result, the user turns out to be available and the functions of the usual mobile phone: voice communication, reception and sending faxes, SMS, etc.
- "All you need for work and nothing superfluous". So you can characterize the position with which the structure of these devices is optimized. Indeed, unlike phones, GPRS modems often have several user-defined outputs that support completely standard interfaces RS-232, USB, etc., as well as connectors for connecting an external antenna and other devices. In addition, many modem have ample opportunities for remotely configure parameters and operational software management of their work. On the other hand, the modems are minimized as much as possible by exclusion from their composition of such unused parts in this case, such as a microphone, speaker, display, keyboard, etc.
- "Performance in the most different conditions" - ensure the designs of modems and the "unpretentiousness" of the parts of them to the supply voltages. Purely constructive, existing GPRS modems can be divided into three groups. In the first of them, which can be conventionally called "office", enter devices made in the form of PC-Card Type II (PCMCIA) focused on connecting and using together with portable computers. The second group can include models intended for embedding in other devices, and therefore differ from the maximum "facilitance" of the design. The third group consists of industrial design models, with, on the contrary, "protected" design, ensuring their reliable operation in a wide range of temperatures, humidity, pressures, vibrations, electromagnetic fields and other types of influences. Such models often have a wide-band (for example, from 5 to 32 V) internal power stabilizer, which provides the ability to directly connect to the most different sources ( Li-ion batteries, side network of car, various industrial devices, etc.). Some models of the last two groups are complemented by other devices (GPS system receiver, analog-to-digital converter, etc.), which further expands their functionality and applications.
The use of GPRS modems and modules to implement "intermower" communications to implement "intermower" communications to the area of \u200b\u200bwhich is a very large circle of various applications: car safety and dwellings, industrial and home automatics, telemetry equipment and parameter control systems and displacements of various objects, mobile Office and much, much more. In other words, GPRS modems may be useful in all cases where the connection cable laying or deploying a specialized wireless system for one or another reasons (organizational, technical, economic) is impossible or inexpedient. It is also important that it is not necessary to obtain any special permission to operate GPRS modems. To use them just just buy SIM card And further pay for the standard GSM operator services.
In general, it should be noted that GPRS, despite the existence and other technologies high-speed transmission data via cellular channels (for example, Cellular Digital Packet Data for D-APS network networks, High Speed \u200b\u200bPacket Data - for systems with code separation of signals according to the CDMaOne standard etc.), due to the current actual world domination GSM, just "doomed" to become For the next decade (to wide distribution of 3G, Wi-Fi networks, etc.) one of the key wireless data transmission technologies.
Igor Skolotnev

To organize Internet access to the PDA or on a laptop today does not constitute special problems. In principle, the laptop is normal computerwhich, as a rule, has all the standard interfaces (Ethernet, USB) or a regular analog modem for commutable access to the public-up telephone line (Dial-Up). With a pocket computer (if, of course, this is not a communicator) will be more complicated - it should have a USB-HUB to connect to a USB modem or some wireless interface (Accordingly, the device organizing the Internet exit must have the same wireless interface).

only, as the PDA, and the laptop - mobile devices, so it would be foolish to let their wires for accessing the Internet. Therefore, let's talk about wireless internet access methods from these mobile devices.

There are several ways to organize mobile wireless Internet access. Of these, the most popular and universal currently in Russia is a cellular connection using a regular GSM phone, which allows you to organize high-speed Internet access on GPRS technology (in this case, the gateway to the network is cellular telephone). However, in this case, sometimes there are problems with the sharing of a laptop and a phone, since it is necessary to use a wired connection (USB or RS-232), which is not very convenient on hiking conditions, or wireless communication (Bluetooth, Infrared, Wi-Fi), What is also not always suited (after all, after all, you still need to talk yet).

GSM / GPRS modem with a USB interface

The cheapest and most universal solution for equipping the PDA or laptop by mobile Internet are GSM / GPRS modems with a USB interface. And today there are quite a lot of such devices.

Some of them are simply GPRS / GPS modems - without the possibility of using the conversation mode, others allow you to connect the Hands-Free headset, with which you can talk on the phone from the computer.

However, despite compactness, such models are not very convenient to use, since "hanging out" on the PDA or laptop through an additional cord requires individual storage, they are lost and generally limit mobility (for example, to use the USB device with the PDA often needed also Additional interface - cradle).

GSM / GPRS PCMCIA card

If you do not have a desire to use a bunch from the phone and a laptop to access the Internet, then you can purchase a special PCMCIA card that allows you to organize high-speed access to Global Network And turns your laptop in a full-featured mobile phone with the ability to negotiate, as well as send faxes and SMS / MMS messages. By the way, keep in mind that for connecting to the Internet GSM operator and the corresponding tariff plan Must support GPRS.

Maps with the PCMCIA interface (PC-Card Type II) today is not so much on sale. Some of them, as well as the above, are simply GPRS / GPS modems without the possibility of using the conversation mode, but this acquisition does not seem successful to us. After all, at the speed of GPRS connections, the use of equipment such as Skype, or other, allowing to talk, can cause delays in speech transmission, and considerable voice traffic will have to pay at GPRS rates, which will certainly be more expensive than the usual call to the mobile phone, which is In another city or even the country.

So more attractive, in our opinion, modems that have a connector for connecting a headset that allows you to talk on the phone from a computer, and simple software for emulation of all the functions of the telephone set - such, for example, as Ovislink WGP-1500, Billionton PCMCIA GPRS / GSM Wareless Modem or Neodrive GPRS-100S (included Passive headset on a special clip - Headphone and sensitive microphone).

From other features of such modems, you can note the presence of two or three GSM bands (GSM 900, 1800, 1900), the convenient location of the SIM card compartment and the original antenna design (it is removable). For example, at the Billionton modem, the antenna design allows either to hide it inside the device, making it as compact as possible, or put forward positioning for better quality reception. A modem NEODRIVE GPRS-100S has an external rotary antenna, but, although its design looks more reliable than the Billionton modem, this device is less compact.

To access the Internet, it is enough to install drivers for the corresponding PCMCIA card and configure the network connection, but if you want to use all the functions of the phone, you need to install a special software. Virtual keyboard And the functions of this software are usually implemented in the familiar "telephone" design and provide a simple function of the dialing and a call to the call. Of course, move on the menu of such a phone on big Screen The laptop is much easier than viewing icons on a small screen cell phone. In addition, such software can provide panels with additional features. You can install a GPRS connection from the program, send SMS, e-mail and fax, as well as manage notebook, synchronize data with the organizer and perform all the operations as on the phone.

To use such a card, as an ordinary mobile phone, you must, of course, connect the included headset (from the microphone and the laptop speakers, these devices do not work). After that, you can respond to incoming calls or call someone, like from the headset of a regular phone. The only difference between the PCMCIA card from the phone with the headset is that the system can only be used while working with a laptop, that is, if the laptop is disabled, then you will fail to use this phone.

GSM / GPRS COMPACTFLASH card

However, the PCMCIA interface is only in laptops, so the PDA with the help of the above-described devices to connect to the Internet will not be possible. But there are more versatile solutions based on CompactFlash interfaces (CF) or Digital Secur (SD), which can be used with both laptops and PDAs.

For example, NEODRIVE has a GPRS-110S model, which is identical to the GPRS-100S model for PCMCIA, but has a CF interface, which allows you to connect it to a pocket computer with such an interface and turn it into a communicator.

GSM / GPRS CF-, SD cards are usually more complicated, and therefore more expensive than GPRS-modems based on PCMCIA. This is due to the need to use additional batterywhich is placed on the device. And to this battery, the additional indication of its condition is required, the possibility of filing external nutrition And the plug for charging. To charge the battery in NEODRIVE GPRS-110S, a special USB adapter is used, which connects to the power connector located from the front side of the device, next to the antenna.

Included with NEODRIVE GPRS-110S on a special clips, a headset is supplied - a headset and a sensitive microphone.

CompactFlash and Security Digital devices are universal - to use them in a laptop, only a special adapter for PCMCIA is needed (NEODRIVE GPRS-110S CF / PCMCIA adapter is included in the package). For the application of the GPRS-110S model, together with the PDA, the Pocket PHONETOOLS program is also included, which is also functional features And the interface is similar to the PHONETOOLS version for a laptop, that is, turns the PDA into a regular cell phone (or rather, to the communicator).

Unfortunately, when using such GPRS modems, it is impossible to connect as a phone wireless headset Bluetooth, even if such an interface has a PDA. The fact is that GSM telephony of such modems only works with their own headsets and does not use the capabilities of the computer.

We conclude that the price of such devices offered on russian market, varies from 100 to 300 dollars.