The emergence in our everyday life useful things that we owe a passionate American inventor, scientist and radio - Alu gross. Although, of course, you might think, "big deal - suggest to use the radio, in fact, for its intended purpose". Everything seems to be correct, but when you consider that this idea was suggested in 1950, the situation becomes quite different. All the electronics at that time was done on lamps, and model army "portable" radio was a backpack satchel weighing about 20 pounds. It is hard to imagine a fan of "amenities" who would agree is a small wired phone to carry around the apartment kind of "chest antenna"! And gross had to work hard to prove that his idea is not absurd, and subsequently to be widely sought after by people, although he could not offer anything better design that received for their size and weight eloquent nickname "the brick".
To get a feel for how the idea of the phone was ahead of its time, suffice it to say that by the time the first production models of home cordless phones - in the early 70-ies of the twentieth century - the period of validity of patents gross has already come to an end! On this occasion, the inventor ironically even joked: "If my patent has not expired, then I'd be a millionaire several times ... and bill gates would stand behind me."
Indeed, cordless phones today are produced in large quantities by a variety of companies, and the convenience and ease of use seems to require no explanation. But this is not always the case, and questions still remain.
The phone worked only at night...
This story happened a few years ago, when in the midst of the white nights in St. Petersburg, I called my old friend and asked the question: "What could happen to the phone during its transportation by plane, he began to work only after sunset?" To be honest, this question has me stumped. I always knew this woman (Humanities education), very attentive and careful person, besides always good and clearly articulating their thoughts, but her question seemed absurd! No, of course, the Sun affects the radio, and this is well known to radio astronomers, and many other experts, but to suspect a home cordless telephone in this sensitivity was absolutely impossible...
From further questioning, I found out that the phone my friend bought during a trip through Europe and even in practice, it was time to check its functioning abroad. But after returning home with the phone was going incomprehensible: a normal conversation was possible only on the distance away from the base, and removing from it in the tube there was a noise, background, and communication was cut off. But with the coming of darkness (which at this time of year in St. Petersburg for a short time only occurs deep in the night) the phone started to work great and you can have walks around the block. The solution to this "mystical" history turned out to be extremely simple, it was enough to compare the intervals of "mood" in the behavior of the phone over time... the first television program. It is the television broadcasting signals (a friend of mine lives near the tower) and interfere with the operation of the phone in the daytime. And the reason for that was the fact that you purchased the phone was designed to work in the frequency range, which in our country are used for TV broadcasting. So ignorance about the differences in the use of radio frequencies in different countries did pretty good phone just a pretty toy.
So what you need to know to avoid this and similar problems?
First of all, it should be borne in mind that cordless phones in our country selected frequencies in the range: 31-40 MHz, 814-960 MHz 1880-1900 MHz. Owners of devices operating at other frequencies may encounter described or other similar situations where the phone will interfere not only neighbors while watching television, but also other organizations that use radio communication. And this is what a serious trouble.
To avoid this, it is not required, going to buy the phone, to learn by heart these values of radio frequencies, and enough to make sure the seller that the phone is approved for use in our country. In this case, you can be assured - with operating frequencies (and other parameters) by the phone all right. Speaking of other parameters. When certification is quite certain requirements apply not only to the working frequencies of the phones, but also to the power of their transmitters, types of antenna used, etc., that is why those who, for example, wanting to increase the range of the phone, starts to make changes, immediately revoke his certificate and run the risk of entering into conflict with the law.
Now on the other features of cordless phones.
First of all, it should be noted that many of the users of the phone are not aware of the fact that, in fact, it is a common coherent radio station, and its signals can be taken by anyone. And when you consider that the vast majority of cordless telephones operating in the first two of these bands, do not have any means of voice encoding, it is possible to eavesdrop on such negotiations can be simply by using a specialized receiver.
Not the best protection and are special "codes" that are exchanged during connection base and the tube is intended to exclude false positives from other signals. All these digital codes are sent over the air in plain text and therefore can be easily intercepted. This fact is based the work, which received a fairly large scale, "podsadecki" tubes, providing the ability pirate connections to databases of other people's phones and keeping conversations at the expense of others.
These shortcomings free standard cordless DECT operating in the range 1880-1900 MHz. These phones work in digital mode and enable processing of signals similar to those adopted in the GSM cell. Generally these phones, can perhaps be regarded as the most promising, especially because some modified version of DECT even included the International telecommunication Union in the number of standards adopted for use in mobile communication systems of the third generation.
Apparently, the only limitation on the use of DECT phones is relatively small range: outdoor up to 300 m, and in buildings and even less - about 30-50 m, and "vertical" is only plus or minus one floor. Although for many purposes such quantities is enough. Another factor, initially preventing the spread of DECT phones in our country, their slightly higher cost is now eroding, because the prices are almost the same.
A little about functions
It should be noted that the number of varieties of different functions and their nuances in today's phones is huge. Therefore, focus only on the core.
More recently, the standard version of the work of cordless phones was mode on a "one base - one tube". It is this set of (base, connected to a telephone line and handset - user) is usually understood by the word "phone". However, now most of the cordless phones provide the ability to connect to several (usually 8) tubes, and "registration" tubing on several (4 or 8) bases. Some handsets can communicate with each other (bypassing the database) as a normal radio station. So now even particularly distinguish these types of radiotelephone equipment as "base with a tube and a secondary tube. Operate the additional handset is exactly the same as main, and they are purchased in cases where there is a need to expand the number of users of the radio telephone. The only thing that must be remembered is that all elements of the radiotelephone must be able to understand each other, i.e. that they are compatible with each other in the parameters. In many cases, they may not only refer to different models of phones, but made by different manufacturers.
Modern models have the majority of traditional phone functions: dialing in pulse and tone mode; the volume in the handset and ringer volume control; Handsfree (speakerphone) button microphone mute; electronic memory (notebook) telephone numbers and keys are "one-touch" dialing and redial the last dialed number; displays (and am on the bases and tubes) for displaying various information - date, time, number, call duration, etc.
But in cordless phones and have specific functions. One of them is the "find handset" - allows the owner of the phone to send the call from the base to which the receiver will respond with an audible signal, allowing its detection. A more advanced variation of this function is the "Intercom" (the connection between the base and the handset to the telephone line), allowing the tube to send the call to the base and talk with the people there, and Vice versa option - a conversation on a call with the base.
Also for specific handsets of cordless phones is the display function of the battery discharge, indicating the need to return the handset to the base for recharging. But we must remember that always keep the handset on the base should not be, as it leads to premature battery failure.
The design of the cordless phones are also very different. Among the interesting design solutions radiotelephones note series of phones Goodwin Lund. They base unit is made as "invisible" and is made in the form of a framework for small images or photographs, which can just be put on a table or hang on the wall and it will participate in the design of the interior.
This is a completely opposite idea is implemented in the design of another group of phones. Models such as Sanyo CLT-2032, LG GT-9540A, 9720, 9751A, 9760A, 9770, a number of Siemens Gigaset models, etc. - contain essentially two phones: wired landline phone, combined with the base unit, and wired up. Such models, allowing you to dial a number and call and from the base, and the tube may be convenient to use a group of people in a family or small workplace.
A common element of modern cordless phones became cassette or a digital answering machine, but the function of establishing an independent voice mailboxes for multiple users in modern devices is not always the case.
Similar progress has occurred and with features such as "Redial" and Baby Call. Previously, many phones do not provide reliable execution of the function of the dial, and reach the goal could only repeatedly pressing the snooze button dialed calls, now this process in most models have been successfully automated. Not less important and the second-mentioned functions. Mode Baby Call allows you to pre-programmed telephone number to be dialed after pressing any key of the phone and is very small child. Here are just along the "Redial" and Baby Call somehow found not in all phones.
Developers have taken care of phones and other function - Baby Phone, you can listen to the room where the child is placed. It is realized using standard mode "Intercom" and the most can be initiated both from the base and the tube.
But for those who prefer to talk on the phone while continuing to do something, at the same time moving around the apartment (for example, during cleaning or cooking dinner) firm Samsung has even released model SP-R6100. Here is a miniature tube (looks much like a cell phone) allows you to connect garniture containing earphone, microphone and answer button on the call. However, the tube can easily be placed in your pocket - all the buttons protected against accidental clicks hinged lid. And when you use the handset without the headset to answer the call simply by opening the cover - push any button is not necessary.
How to choose a cordless?
Well, first of all, we can say that for home you can choose any phone that You just will like. The only caveat should be made here regarding phones range of 31 - 40 MHz: at their location near the TV or computer connections may experience interference. If the most important range of communication - the choice should be made among the phones for the 900 MHz band. Well, for office, of course, better to buy phones DECT standard, distinguished by the abundance of opportunities, including the functions of the PBX.
As for the choice among different brands and manufacturers, now it is is not very important. The point here is that with the current level of development of microelectronics and international cooperation, the most similar devices from different manufacturers to be made on the basis of very similar technical solutions, or simply on the basis of the same sets of integrated circuits. And when you consider that the process of assembling serial products is usually extremely automated, it becomes quite no matter where geographically located production. Thus, the reliability of different models is virtually identical. The exception here could be just any little-known company, in order to save, for example, do not produce the required quality control used parts and finished products. Here are the purchase of such products should be avoided. To this group belong the so-called "refurbished" phones that have already been exploited for some time, and then in small workshops were trivial washed, refurbished and put on sale. To distinguish such devices can be either because they are already outdated or the presence of additional marking the company, by whose order they were made and where it was used. At the time of sale all these phones usually work fine, but their technical resource already thoroughly exhausted. Notice this shortcoming buyers only after some time by rapidly discharge the battery, nesrabatyvaemoy buttons, declining range and resultant damage.
In General, in order to choose the right phone, it is necessary to accurately identify those requirements that it must meet. Therefore, turning to specific models, taking into account the comments made, we can give the following General recommendations.
If you need to acquire as cheap phone, then you should pay attention to, for example, models such as the Alcatel One Touch First 10 and 20, LG GT-9160 and GT-7101, Panasonic KX-TC1005RU, KX-TC1019RU, KX-TC1025, KX-TC1045, KX-TC1403, KX-TS, KX-TC1455, KX-TCD951, Philips KALA 6120, Sanyo CLT-138, CLT-538 and Siemens Gigaset 100.
If under the terms of use the most important parameter of the phone is its range, it is possible to recommend the production of phones LG models GT-9130, GT-9140A, GT-9540A. Claimed for them, the range of work in rooms up to 400 m, which guarantees communication even within very large buildings.
Well, if you want to use the most feature-rich phone, this may be one of the following models: LG GT-7710, LG GT-9771A, LG GT-9780, Panasonic KX-TCD735RU-M or Siemens Gigaset 3035.
Publication: www.cxem.net