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What are the differences between synchronous modems and asynchronous modems?
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Why the synchronous modems are more costly than the asynchronous modems?
Because they contain clock recovery circuits
What is syncronous modem?
Synchronous and Asynchronous data transfer are two methods of sending data over a phone line. In synchronous data transmission, data is sent via a bit-stream, which sends a group of characters in a single stream In order to do this, modems gather groups of characters into a buffer, where they are prepared to be sent as such a stream. In order for the stream to be sent, synchronous modems must be in perfect synchronization with each other. They accomplish this by sending special characters, called synchronization, or syn, characters. When the clocks of each modem are in synchronization, the data stream is sent. In asynchronous transmission, data is coded into a series of pulses, including a start bit and a stop bit. A start bit is sent by the sending modem to inform the receiving modem that a character is to be sent. The character is then sent, followed by a stop bit designating that the transfer of that bit is complete.
What Asynchronous voice band modems?
Synchronous modems operates in the audio domain, at rates up to 28800 bps in audio lines, used in telephones systems (using synchronous data). The usual modulation methods are the phase modulation and integrated phase and amplitude (at higher rates than 4800 bps).In synchronous modems, equalizers are used, in order to offset the misfit of the telephone lines. These equalizers are inserted in addition to the equalizers, that sometimes already exist in the telephone lines.These equalizers can be classified into three main groups:Fixed/statistical equalizer - these equalizers offset the signal according to the average of the known attenuation in each frequency. Tuning the equalizer is sometimes done in the factory and stays fixed, usually they are used to operate at low rates in a dial up line.Manually adjusted equalizer - these equalizers can be tuned to optimal performance to a given line. These equalizers should be re-tuned when the line is replaced and periodically. Specially, it should be tuned frequently when the line is of a low quality and it's parameters are changed frequently. Tuning is done using a button inside the modem (or on the external board).Automatic equalizer - these equalizers are tuned automatically when the connection is established. Depending on the line quality in a specific moment, in a process of about 15ms to 25ms, after the first tuning, the equalizer samples the line continually and adjusts itself to the changed conditions, so the modem operates at each moment under optimal conditions. The fitness process operates, in some modems, at rates of 2400 times in a second.Synchronous modems operate in the same manner asynchronous modems. However, synchronous modems operates at higher rates and since the requirements to transmit at these rates is increasing, most of the innovations are implemented for synchronous modems.In synchronous modems the channel can be split for several consumers at various speeds. Modems who have this ability are called SSM - Split System Modem. These modems can use a simple split or a split using multipoint connection.Synchronous data is accompanied by a clock signal. Synchronous data is almost always grouped in blocks, and it is the responsibility of the data source to assemble those blocks with framing codes and any extra bits needed for error detecting and/or correcting according to one of many different protocols (BISYNC, SDLC, HDLC, etc.). The data source and destination expect the modem to be transparent to this type of data, conversely, the modem can ignore the blocking of the data.
How many wires are in rs232?
The full original standard defined by the telephone company for connecting 300 baud full-duplex, 1200 baud half-duplex, asynchronous, synchronous, etc. modems to data terminals defines 25 wires. However many of these wires serve very specialized purposes or have become obsolete with improved modems.Later the standard was modified to permit a subset of the 9 wires most frequently used by asynchronous modems: chassis ground, signal ground, transmit data, receive data, request to send, clear to send, data set ready, data terminal ready, and ring detected.Many applications can get away with using the bare minimum of 3 wires: signal ground, transmit data, and receive data.
What are the four generic architectural components of a public communication network?
Subscribers: the devices that attach to the network, such as telephones and modems. Subscriber line: the link between the subscriber and the network. Exchanges: the switching centers in the network. Trunks: the branches between exchanges. Trunks carry multiple voice-frequency circuits using either FDM or synchronous TDM. By: khurram, sibbi Pakistan
What are the two forms of modems?
The two forms of modems are dial-up modems and private line modems
What are the two kinds of modem?
Modems come in two varieties :Internal modems are the modems that are fixed within the computer.External modems are the modems that are connected externally to a computer as other peripherals are connected.
What is the difference between a pc modem and modem?
Nothing. They are both modems (MOdulator/DEModulator).
What are the differences between analog and digital modems?
Analog modems use the telephone cable to send audio signals, which represent 1's and 0's over a connected phone line, using phone voltages. Digital modems use a high frequency signal with the data superimposed on it. They can use the copper phone wires like an antenna. In this way there does not have to be phone connection in use. The phone can be used as well as the signal, if a filter is used to stop interference. Digital modems can also use fibre optic or coaxial cables.
What is the difference between the Arris TM722A and the Arris TM722G modems?
The TM722G has a battery backup option.
How many types of land line modem are there?
There are several types of land line modems that have been created over the years. Some of the more dated modems were soft modems as well as dial up modems.
How many types of land line modem?
Soft modems and dial up modems are some of the more dated modems that were created. They are considered to be land line modems since they used wired connections and ports.
