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U-90E Data/Fax Modem
DCD: Data Carrier Detected - a control signal line of the RS-232C interface.
DCE: Data Circuit Terminating Equipment or Communications Equipment - a modem is a DCE.
Demodulation: Transferring analog signals into digital data bits.
Digital: Digital data consists of a series of bits. A bit may have only one of two states. Analog data may have
any value.
Digital loopback test: A modem test procedure which transfers the received digital data back to the
modulator and transmits them out.
DIP switch: Dual inline package switch. DIP switches are abundant in the world of electronic equipment. They
are used to set certain parameters on a printer, modem or other peripheral devices. You will not find any DIP
switches in ZyXEL modems. ZyXEL modems let you perform all settings from the front panel or through
command sequences.
DLE: The ASCII code that is used in voice data mode to separate data segments from command segments.
DSP: Digital signal processor. ZyXEL modems are equipped with this/these device(s). DSPs generate,
process and analyze all signals.
DSR: Data Set Ready - a control signal line of the RS-232C standard.
DTE: Data Terminal Equipment - a computer or a terminal.
DTMF: Dual Tone Multi-Frequency. The technology used in pushbutton telephones, commonly known as
touchtone, of generating audible notes to represent numbers.
DTR: Data Terminal Ready - a control signal line of the RS-232C standard interface. Some computers set this
signal when they are turned on, even if they are not able to receive data.
Echo: For a modem user, echo has two meanings: A modem can return all received characters to its local
terminal/computer so they can be seen on-screen. The other meaning of the term ``echo'' is that part of the
analog signal the modem sent out is bounced back by the telephone network to the modem's receiver, mixing
there with the remote modem's signal.
EDR: Extended Distinctive Ring - A feature of ZyXEL modems which helps to distinguish between data, fax
and voice calls.
EEPROM: An Electronically Erasable and Programmable Read Only Memory. Such a device is used in ZyXEL
Glossary
C
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