DNIS (DIRECTORY NUMBER IDENTIFICATION SERVICE): DNIS is a feature of 800 and 900 lines
that provides the number of the caller dialed to reach the attached computer telepho ny sys tem. Usin g DNIS
capabilities, one trunk group can be used to serve multiple applicat ions. The DNIS number can be pro vid ed
in a number of ways, inband or out-of-band, ISDN or via a separate dedicated data channel.
DPO (DIAL PULSE ORIGINATION) CHANNEL UNIT
DPT (DIAL PULSE TERMINATING) CHANNEL UNIT
DROP & INSERT (D&I): As applied to T1, D&I refers to the process whereby one DS-0 channel is de-
multiplexed out of the DS-1 synchronous bit stream at one port of a digital channel back and another DS-0
inserted back in. The Windows-based Remote Monitor software program can be used to perform D&I on
individual channels between two T1 lines connected to the Access Bankô II.
DSU/CSU (DATA SERVICE UNIT/CHANNEL SERVICE UNIT): A device terminating a digital chan-
nel on a customer’s premises where it performs line coding, line conditioning and equalization functions
while responding to the receipt of loopback codes sent from the Central Office (CO) A DSU/CSU sits be-
tween the digital line coming in from the CO and devices such as channel banks or data communications
devices.
DSX (DIGITAL SYSTEM CROSS-CONNECT frame): A bay or panel to which T1 lines and DS1 cir-
cuit packs are wired that permits cross-connections by patch cords and plugs. A DSX pa nel is used in s mal l
office applications where only a few digital trunks are installed.
DTE (DATA TERMINAL EQUIPMENT): In the EIA/TIA 232E standard specification, the RS232 inter-
face is connected between the DCE (Data Circuit-Terminating Equipment) and the DTE. The main differ-
ence between the DCE and the DTE is the pins two and three are reversed. The ABII uses an RS-232 port
for management and asynchronous and synchronous data transmission.
DTMF (DUAL TONE MULTIFREQUENCY SIGNALING): A method of signaling in which a combina-
tion of two frequencies out of a possible eight are used to t ransmit numerical address informat ion. The eight
possible frequencies are 697 Hz, 770 Hz, 852 Hz, 941 Hz, 1209 Hz, 1336 Hz, 1477 Hz, and 1633 Hz.
E&M SIGNALING: A signaling arrangement that uses separate leads, called resp ectively the E lead an d
the M lead, for the signaling and voice signals. The M lead (derived from ‘Mouth’) transmit s ground or b at-
tery to the distant end of the circuit, while incoming signals are received as either a grounded or open con-
dition on the E (derived from ‘Ear’) lead. The E&M tie trunk interface functions as a de facto standard in
the PBX - T1 multiplexer Telco environment.
ESF (EXTENDED SUPERFRAME FORMAT):
FACILITY DATA LINK (FDL): The 4 Kbps channel used to transmit supervisory
FOREIGN EXCHANGE CHANNEL UNIT - OFFICE END (FX0)
FOREIGN EXCHANGE CHANNEL UNIT - STATION END (FXS)
FRAME RELAY ACCESS DEVICE (FRAD):
FXSDN (FXS SOFTWARE-DEFINED):
LINE INTERFACE UNIT (LIU): Typically, a controller device in a D-type channel bank, such as th e CAC