Device driver: Software that controls how a computer communicates with a device, such as a printer or mouse.
Digital signal: Digital devices, such as terminals and computers, transmit data as a series of electrical pulses which have discrete jumps rather than gradual changes.
Digital Transmission: A method of electronic information transmission common between computers and other digital devices. Analog
signals are waveforms: a combination of many possible voltages. A computer's digital signal may be only "high" or "low" at any given time. Therefore, digital signals may be "cleaned up" (noise and distortion removed) and amplified during transmission.
DIP switch (pronounced "dip switch"): A set of tiny toggle switches, built into a DIP (dual
DPSK (Differential Phase Shift Keying): A common form of phase modulation used in modems. It does not require complex demodulation circuitry and is not susceptible to random phase changes in the transmitted waveform, thus reducing errors during transmission.
DSR (Data Set Ready): An RS232 signal sent from the modem to the computer or terminal indicating that it is able to accept data. Contrast with DTR.
DTE (Data Terminating Equipment): A term used to include any device in a network which generates, stores or displays user information. DTE is a telecommunications term which usually refers to PCs, terminals, printers, etc.
DTMF
DTR (Data Terminal Ready): An RS232 signal sent from the computer or terminal to the modem indicating that it is able to accept data.
E
EBCDIC (Extended Binary Coded Decimal Interexchange Code) (pronounced "eb suh dick"): An IBM character code used in its mainframe and midrange computers. It is an
Echo: The reflection or duplication of a signal back toward its source. Echoing is useful when a terminal is transmitting data, in that the data can be echoed to the screen so the user can monitor what is being sent. Echoing is undesirable when it refers to the signal which results on a telephone line from impedance mismatches.
Echo cancellation: A high speed modem technique that isolates and filters out unwanted signals caused by echoes from the main transmitted signal. This allows
EIA (Electronics Industries Association): A membership organization founded in 1924 that includes manufacturers of electronic parts and systems. With over 1200 members, it sponsors shows and seminars and gives awards for outstanding contributions in electronics. It sets electronic interface standards, such as
Environment: A computer configuration that includes the CPU model and system software (operating system, data communications and database systems). It may also include the programming language used. It sets the standards for the applications that run in it.
EPROM (Erasable Programmable Read Only Memory) (pronounced "eeprom"): A reusable PROM chip that holds its contents until erased under ultraviolet light.
Error correction: The process of detecting distorted data bits and requesting a retransmission or interpretation to correct the error. Errors are introduced by bad line conditions or external interface.
F
Fax (facsimile): Refers to the
Firmware: A category of memory chips that hold their content without electrical power, they include ROM, PROM, EPROM and EEPROM technologies. Firmware becomes "hard software" when holding program code.
Flash Memory: A memory chip that holds its content without power, but must be erased in bulk. The term comes from its ability to be erased "in a flash". Flash memory is derived from EEPROM, but are less expensive and provide higher bit densities.
Flow control: The process of regulating the speed at which data enters or leaves a serial port. Software flow control is implemented by communications software or by the user sending predefined characters or packets which are recognized as "pause" and "resume" indicators. Hardware flow control is achieved by using the RTS (request to send) and the CTS (clear to send) control lines of the RS232 interface.
Footprint: The desk or floor surface that a piece of hardware occupies. Also referred to as "real estate".
Foreground: The application program currently running on and in control of the PC screen and keyboard. The area of the screen that occupies the active window. Compare with background.
Format:
1.The way text is set up on a page.
2.To prepare a disk for holding information. Formatting a disk can delete all information that was previously on it.
3.The way information is structured in a file, often specific to one application or protocol.