MODEM

THE MODEM - a functional device, providing inflexion and демодуляцию signal; the device converting digital signals in analog form and back for issue them on communication link of the analog type.(the extract from explanatory dictionary on informaticses).

Presently we all observe the computer boom in the field of telecommunication, network develop with enormous velocity, which as gigantic web wind around the world (some see in this threat).But is assigned question: On facility what so much for can occur? As private user of the personal computer can get into enormous world of world information? The Answer forgive;pardon: By means of modem , - a small device near by computer and telephone line or even board idle time in computer. The Modems all intensify and intensify their own functions, modems already even send and take the faxes, what know that waits them in the future. The Market modem enlarges. One generation modem changes another, send rate to information all grow and grows. The Modem is a stair to the general information space. Exactly on this I was shown interesting and useful to study this progressive and important subjects in computer world. Certainly exists several such that, which are also found in tempestuous development (for instance multimedia), but anyway they are connected with modem and their use.

Begin consideration a modem I want first of all with explanations their external indicator.(I рассмотрю only indicators external modem since internal usually they do not possess).

HS (High velocity)

This indicator works constantly at determination you relationship on the largest velocity, available your modem. In some modem indicator works in pulsing mode. The Big part indicator HS remains in working order since time of the determination relationship on high velocity before the following session.(though for exact determination of its modem better addresses to manual of the user.

AA (Autoanswer / answer to call)

Work of this indicator speaks of readiness of the modem to answer received call.

State of working

It Is Included directly before that, as modem answers call. In some model for time relationship with the other abonent this indicator отключаетсядругие modems leave the indicator included on length whole communication link.

CD (Discovered carrier)

Work of this indicator speaks of that that your modem left in mode relationship with removed by modem. The Modem reads the signals carrying other modem, and two modems begin the communication link between itself. It Is Actuated at determination relationship on telephone line and at the beginning initially communication link between two modems. The Modems, truth, can talk on different languages, however on functioning(working) the indicator this does not affect.

OH (Initiation of the telephone call)

Cut-in of this indicator speaks of that that modem left in telephone line and ready to realize the set of the number for the reason determinations relationship with the other modem. Approximately in the same way, as this occurs the tube of the telephone set when removing. It Is Included at initiations of the telephone call and under successful join and determination of the dialogue mode with the other modem. One, rings you, will hear in this time signal occupied .

RD (Acceptance data)

This indicator operates at reception by modem of each bit data. It Is Included in dialogue modes when sending its menu removed by computer and the other information, as well as, when you will use its modem for receiving and boot the file. If process of the boot the file exceeds installed time, indicator will prompt you about this.

SD (Sending data)

This indicator operates when sending of each bit data. During session with the other modem, at issue of information on the other computer. During issue indicator помигивает or is constantly enclosed.

TR (Readiness terminal data)

The Indicator fires under included modem and his(its) work with software and computer. The Computer on consequent cable sends on modem of the signal DTR. The Indicator active when loading of software of the modem, included feeding and under steady work device.

MR (Modem ready to work)

The Indicator operates when enabling modem and at connection him(it) to network. When enabling the modem. But in the same way under самотестировании.

More Wide-spread indicators of the condition of the modem

RS ( Inquiry for sending data)

This indicator works when sending by computer of the signal RTS on modem ( depending on desksides AT- commands). It Is Included during communication link, when computer requires the modem of the sending data begin about.

CS (Sending to information)

Operates under the repeated sending data, depending on desksides AT-commands. In in time relationship , when modem reports the computer that possible to begin sending data.

SYN (Synchronous mode)

The Modem works in synchronous mode. This rather rare state of working personal computer, used greater machine and special device ( as , for instance, answerbacks). During communication link in synchronous mode.

Indicator of the mode to correction mistake (ARQ) and fax mode (Fax)

Work of this multifunction indicator speaks of that that is discovered signal to correction mistake on the other end relationship and modem works in this mode. The Indicator also marks that modem functions in fax mode. During communication link in mode of the correction mistake under corresponding to desksides AT-commands. The Flashing of the indicator ARQ/FAX. Points to functioning(working) the modem in mode of the sending or receiving the fax messages.

LB (Low voltage of the battery of the modem)

Points to low voltage of the portable battery of the modem. At discharge of the batteries of the battery.

Other specific indicators

Such indicators possible to meet on some model modem only.

TXD (Data communication)

The Indicator data communication by modem through serial port of the computer.

RXD (Acceptance data)

The Indicator of the acceptance given on serial port of the computer.

EC (Mistake Management)

The Indicator functions when functioning(working) in mode of the correction mistake or compressions data.

SQ (Quality of the signal)

The Indicator qualitative communication link; blinks under mediocre join.

TST  (Testing)

The Indicator of the execution by modem самотестирования.

Modemnye standards

Now I want to consider the standards a modem, but before this I want to say what company these standards have installed and install:

1. The First standards in the field of telephony, electronicses and computing machinery were installed by committee of the company AT&T.
2. The Company Microcom Networking Protocol (her(its) standard known under name MNP).
3. CCITT (Comite Consultatif International de Telegraphique et Telephonique) - An International consulting committee on telegraphies and telephony, representative to take the protocols in international scale.
4. The Standards Class 1, Class 2, and Class 2.0, is designed assotiation of the industrial facilities telecommunication (Telecommunications Industry Association, TIA).
5. The Standard CAS, is created by common efforts to corporations Intel Digital Communications Associates.
6. The Standard SendFax is designed company Sierra Semiconductor. (the cost SendFax-modem earlier was below cost of the equipment vastly, capable what send, so and take the messages. But now if only you do not continue to use SendFax- modem, with which you why-that miserable растаться, no no reasons to worry about support of this standard communication програмным by provision)

Some compatibility

Hayes-compatibility

The Term Hayes-compatibility is not correct, since Hayes-standard exists much, but better all таки to have a modem with this compatibility, since this will simplify work in the future.

Speech compatibility

Many modems today work in mode fax device. Appear in the same way models with speech terminal. Some are an суперсовременные modems, as, for instance, series modem ZyXEL U-1496, have a possibility of the reproducing the voice, recorded mode in цифровом. Such features allow to use the modems as answerback when selecting corresponding to communication program. The Speech message is saved in the manner of file on computer and for his(its) задействования necessary to assign the program special command for reproducing. Since sound files occupy on hard disk plenty of room, that modems ZyXEL use compression speech signal in purpose spare place on hard disk

Switch speech \ data

The Modems of the company US Robotics Courier, modems ZyXEL U-1496, and some other models are provided with by switch speech \ data, which allows to choose or, speech mode relationship, or work with given during communication link. The Majority such modem enable the communication program to execute switching or produce самотестирование and the other functions.

Author: А. V. Savin It Is Added: 03.05.2007