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Data Terminal Ready
Data Terminal Ready (DTR) is a control signal in RS-232 serial communications, transmitted from data terminal equipment (DTE), such as a computer, to data communications equipment (DCE), for example a modem, to indicate that the terminal is ready for communications and the modem may initiate a communications channel. The DTR signal is present on pin 20 of the 22-wire RS-232 interface using a DB-25 connector, and on pin 4 of a newer DE-9 serial port. The signal is asserted (logic "1") by raising the voltage of the pin from negative to positive. Dropping the signal back to its negative state indicates to the modem that the communications session shall be terminated. Signaling for modems The DTR signal is an important call control signal for a data modem. According to the RS232 standard, dropping DTR from active to inactive for at least two seconds tells the modem to disconnect (end) a call or data connection. When a modem is being used for automatic answering (such as with the comm ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Control Signal
In telecommunication, signaling is the use of signals for controlling communications. This may constitute an information exchange concerning the establishment and control of a telecommunication circuit and the management of the network. Classification Signaling systems may be classified based on several principal characteristics. In-band and out-of-band signaling In the public switched telephone network (PSTN), in-band signaling is the exchange of call control information within the same physical channel, or within the same frequency band, that the telephone call itself is using. An example is dual-tone multi-frequency signaling (DTMF), which is used on most telephone lines to customer premises. Out-of-band signaling is telecommunication signaling on a dedicated channel separate from that used for the telephone call. Out-of-band signaling has been used since Signaling System No. 6 (SS6) was introduced in the 1970s, and also in Signalling System No. 7 (SS7) in 1980 which became ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RS-232
In telecommunications, RS-232 or Recommended Standard 232 is a standard originally introduced in 1960 for serial communication transmission of data. It formally defines signals connecting between a ''DTE'' (''data terminal equipment'') such as a computer terminal, and a ''DCE'' (''data circuit-terminating equipment'' or ''data communication equipment''), such as a modem. The standard defines the electrical characteristics and timing of signals, the meaning of signals, and the physical size and pinout of connectors. The current version of the standard is ''TIA-232-F Interface Between Data Terminal Equipment and Data Circuit-Terminating Equipment Employing Serial Binary Data Interchange'', issued in 1997. The RS-232 standard had been commonly used in computer serial ports and is still widely used in industrial communication devices. A serial port complying with the RS-232 standard was once a standard feature of many types of computers. Personal computers used them for connection ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Modem
A modulator-demodulator or modem is a computer hardware device that converts data from a digital format into a format suitable for an analog transmission medium such as telephone or radio. A modem transmits data by Modulation#Digital modulation methods, modulating one or more carrier wave signals to encode digital information, while the receiver Demodulation, demodulates the signal to recreate the original digital information. The goal is to produce a Signal (electronics), signal that can be transmitted easily and decoded reliably. Modems can be used with almost any means of transmitting analog signals, from light-emitting diodes to radio. Early modems were devices that used audible sounds suitable for transmission over traditional telephone systems and leased lines. These generally operated at 110 or 300 bits per second (bit/s), and the connection between devices was normally manual, using an attached telephone handset. By the 1970s, higher speeds of 1,200 and 2,400 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DB-25
The D-subminiature or D-sub is a common type of electrical connector. They are named for their characteristic D-shaped metal shield. When they were introduced, D-subs were among the smallest connectors used on computer systems. Description, nomenclature, and variants A D-sub contains two or more parallel rows of pins or sockets usually surrounded by a D-shaped metal shield that provides mechanical support, ensures correct orientation, and may screen against electromagnetic interference. D-sub connectors have Gender of connectors and fasteners, gender: parts with pin contacts are called ''male connectors'' or ''plugs'', while those with socket contacts are called ''female connectors'' or ''sockets''. The socket's shield fits tightly inside the plug's shield. Panel mounted connectors usually have #4-40 UNC (as designated with the Unified Thread Standard) Jackscrew#In_electronic_connectors, jackscrews that accept screws on the cable end connector cover that are used for locking ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DE-9
The D-subminiature or D-sub is a common type of electrical connector. They are named for their characteristic D-shaped metal shield. When they were introduced, D-subs were among the smallest connectors used on computer systems. Description, nomenclature, and variants A D-sub contains two or more parallel rows of pins or sockets usually surrounded by a D-shaped metal shield that provides mechanical support, ensures correct orientation, and may screen against electromagnetic interference. D-sub connectors have gender: parts with pin contacts are called ''male connectors'' or ''plugs'', while those with socket contacts are called ''female connectors'' or ''sockets''. The socket's shield fits tightly inside the plug's shield. Panel mounted connectors usually have #4-40 UNC (as designated with the Unified Thread Standard) jackscrews that accept screws on the cable end connector cover that are used for locking the connectors together and offering mechanical strain relief, and can ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ITU-T
The ITU Telecommunication Standardization Sector (ITU-T) is one of the three sectors (divisions or units) of the International Telecommunication Union (ITU). It is responsible for coordinating standards for telecommunications and Information Communication Technology such as X.509 for cybersecurity, Y.3172 and Y.3173 for machine learning, and H.264/MPEG-4 AVC for video compression, between its Member States, Private Sector Members, and Academia Members. The first meeting of the World Telecommunication Standardization Assembly (WTSA), the sector's governing conference, took place on 1 March of that year. ITU-T has a permanent secretariat called the Telecommunication Standardization Bureau (TSB), which is based at the ITU headquarters in Geneva, Switzerland. The current director of the TSB is Chaesub Lee (of South Korea), whose first 4-year term commenced on 1 January 2015, and whose second 4-year term commenced on 1 January 2019. Chaesub Lee succeeded Malcolm Johnson (Director), Malc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microsoft
Microsoft Corporation is an American multinational technology corporation producing computer software, consumer electronics, personal computers, and related services headquartered at the Microsoft Redmond campus located in Redmond, Washington, United States. Its best-known software products are the Windows line of operating systems, the Microsoft Office suite, and the Internet Explorer and Edge web browsers. Its flagship hardware products are the Xbox video game consoles and the Microsoft Surface lineup of touchscreen personal computers. Microsoft ranked No. 21 in the 2020 Fortune 500 rankings of the largest United States corporations by total revenue; it was the world's largest software maker by revenue as of 2019. It is one of the Big Five American information technology companies, alongside Alphabet, Amazon, Apple, and Meta. Microsoft was founded by Bill Gates and Paul Allen on April 4, 1975, to develop and sell BASIC interpreters for the Altair 8800. It rose to do ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hayes Microcomputer Products
Hayes Microcomputer Products was a U.S.-based manufacturer of modems. The company is well known for the Smartmodem, which introduced a control language for operating the functions of the modem via the serial interface, in contrast to manual operation with front-panel switches. This ''smart modem'' approach dramatically simplified and automated operation. Today almost all modems use a variant of the Hayes command set. Hayes was a major brand in the modem market from the introduction of the original 300 bit/s Smartmodem in 1981. They remained a major vendor throughout the 1980s, periodically introducing models with higher throughput. Their competition through this period was primarily from two other high-end vendors, US Robotics and Telebit, while other companies mostly sold into niches or were strictly low-end offerings. In the early 1990s a number of greatly cost-reduced high-performance modems were released by competitors, notably the SupraFAXModem 14400, which eroded price point ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Null Modem
Null modem is a communication method to directly connect two DTEs (computer, terminal, printer, etc.) using an RS-232 serial cable. The name stems from the historical use of RS-232 cables to connect two teleprinter devices or two modems in order to communicate with one another; ''null modem'' communication refers to using a crossed-over RS-232 cable to connect the teleprinters directly to one another without the modems. It is also used to serially connect a computer to a printer, since both are DTE, and is known as a ''Printer Cable''. The RS-232 standard is asymmetric as to the definitions of the two ends of the communications link, assuming that one end is a DTE and the other is a DCE, e.g. a modem. With a null modem connection the transmit and receive lines are crosslinked. Depending on the purpose, sometimes also one or more handshake lines are crosslinked. Several wiring layouts are in use because the null modem connection is not covered by the RS-232 standard. Origins ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Data Carrier Detect
Data Carrier Detect, abbreviated as DCD, or alternately Carrier Detect abbreviated as CD, is a control signal present inside an RS-232 serial communications cable that goes between a computer and another device, such as a modem. This signal is a simple "high/low" status bit that is sent "from DCE to DTE", or in a typical scenario, from the peripheral to the computer. It is present on virtually all PC serial ports - pin 1 of a nine-pin ( DE9) serial port, or pin eight over a 25-pin (DB25) port. Its purpose varies depending on the device connected, but the most specific meaning is to indicate when a modem is connected to another remote modem via telephone lines. The word "carrier" is a reference to the analog carrier signal generated by a modem, which is modulated to carry the data. On a data modem, the carrier's loss equates to the connection's termination. Much like the Ring Indicator signal, on a PC's serial port, changes to the DCD signal state can generate a hardware interrupt ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Flow Control (data)
In data communications, flow control is the process of managing the rate of data transmission between two nodes to prevent a fast sender from overwhelming a slow receiver. Flow control should be distinguished from congestion control, which is used for controlling the flow of data when congestion has actually occurred. Flow control mechanisms can be classified by whether or not the receiving node sends feedback to the sending node. Flow control is important because it is possible for a sending computer to transmit information at a faster rate than the destination computer can receive and process it. This can happen if the receiving computers have a heavy traffic load in comparison to the sending computer, or if the receiving computer has less processing power than the sending computer. Stop-and-wait Stop-and-wait flow control is the simplest form of flow control. In this method the message is broken into multiple frames, and the receiver indicates its readiness to receive a fra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RS-422
RS-422, also known as TIA/EIA-422, is a technical standard originated by the Electronic Industries Alliance that specifies electrical characteristics of a digital signaling circuit. It was meant to be the foundation of a suite of standards that would replace the older RS-232C standard with standards that offered much higher speed, better immunity from noise, and longer cable lengths. RS-422 systems can transmit data at rates as high as 10 Mbit/s, or may be sent on cables as long as at lower rates. It is closely related to RS-423, which uses the same signaling systems but on a different wiring arrangement. RS-422 specifies differential signaling, with every data line paired with a dedicated return line. It is the voltage difference between these two lines that define the mark and space, rather than, as in RS-232, the difference in voltage between a data line and a local ground. As the ground voltage can differ at either end of the cable, this required RS-232 to use signals with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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