User manual
DS1
Digital Signal Level 1. Framing specication used in transmitting digital signals at 1.544-Mbps
on a T1 facility (United States) or at 2.108-Mbps on an E1 facility (Europe).
DTMF
Dual Tone Multi Frequency. The signal a telephone company receives when a telephone’s touch
keys are pressed. Also known as Touchtone.
E1
European digital trunk standard for 2.048Mbps transmission; an E1 trunk carries 30 64Kbps voice
or data channels, plus two 64Kbps signaling and framing channels.
E&M
RecEive and TransMit. A trunking arrangement used for two-way switch-to-switch or
switch-to-network connections. It is used with E1 and T1 interfaces.
Echo Cancellation
A technique used in high speed modems and voice circuits to isolate and lter out unwanted
signal energy caused by echoes from the main transmitted signal.
Flash
While the phone is off-hook, quickly pressing and releasing the ash hook to signal the central
ofce or PBX that you are requesting special processing, for example, call waiting.
Flash hook
The plunger the phone’s handset rests on while on-hook.
FSK (frequency-shift keying)
Frequency modulation in which the modulating signal shifts the output frequency between
predetermined values.
FXO (Foreign Exchange Ofce)
FXO interface connects to the Public Switched Telephone Network (PSTN) central ofce
and is the interface offered on a standard telephone. FXO interface is an RJ-11 connector
that allows an analog connection at the PSTN’s central ofce or to a station interface on a PBX.
FXS (Foreign Exchange Station)
FXS interface connects directly to a standard telephone and supplies ring, voltage, and dial tone.
FXS interface is an RJ-11 connector that allows connections to keysets, and PBX.
Ground Start
A method of signaling from a terminal or subscriber loop to a switch, in which method one side
of a cable pair is temporarily grounded.
HDB3
A modied AMI signaling code that only applies to E-1 and is used to preserve one’s density
on the line.
Hunt group
A hunt group is a set of phone lines that you can access by using a single phone number.
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User Manual
Public Switched Telephone Network (PSTN) Simulators