Communications Systems Glossary

Echo.  Echo is the reflection of a transmitted signal, normally from the circuit termination at the receiving end.

Echo cancellation.  Modern long-distance telephone circuits employ echo cancellation to prevent the energy in a speaker’s voice being reflected from the receiving end and returning to the speaker to be heard as an echo of their own voice.

Echo suppressor.  An echo suppressor is a device that allows a transmitted signal to pass in one direction only as a method of minimising the effect of echo.

Effective isotropic radiated power (EIRP).  Effective isotropic radiated power (EIRP) is the equivalent power of a transmitted signal in terms of an isotropic (omnidirectional) radiator.

Electromagnetic interference (EMI).  Electromagnetic interference (EMI) is the interference caused by the presence of electromagnetic radiation.

Encryption.  Encryption is a process in which transmitted data (plain text) is scrambled (encrypted) into cipher text at the transmitter and reconstructed into readable data (plain text) at the receiver.

Equalisation.  Equalisation is one of a range of techniques employed to compensate for distortion introduced in a channel.

Error detecting code (EDC).  An error detecting code is a code by which data can be encoded so that the receiver can detect the presence of the errors.

Error detection and correction.  A critical aspect in data transmission is the determination of whether the received data is error-free. To do this some form of error protection, or error detection and correction is utilised.

Error rate.  The error rate is the ratio of the number of data bits received in error to the total number of data bits transmitted.

Ethernet.  Ethernet is a local area network (LAN) implementation using the carrier-sense multiple access (CSMA/CD) protocol on a bus topology.

Extended Binary-coded Decimal Interchange Code (EBCDIC).  Extended Binary-coded Decimal Interchange Code (EBCDIC) is an eight-bit code developed by IBM to represent 256 characters and numbers of information.

Extremely high frequency (EHF).  The extremely-high-frequency (EHF) band is a radio-frequency (RF) frequency in the band 3-30 GHz.

Extremely low frequency (ELF).  The extremely-low-frequency (ELF) band is the radio-frequency (RF) band between 30-300 Hz. The ELF band is not of significant use in communications due to the extremely small bandwidth available and the enormous antennas required.

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