Specifications

T
T1 Digital Carrier Transmission Option (For Domestic U.S.A.
Applications)
The T1 digital carrier transmission option is a domestic U.S.A. option that allows up to 24 channels of voice
and/or data transmissions over a single four-wire cable using multiplexing techniques in superframe (SF) or
extended superframe (ESF) format. For convenience, a customer service unit (CSU) is built into the T1 option
board to terminate the T1 channels, provide protection from transient voltages, and respond to loopback
requests from the central office.
Installers can place up to six T1 boards in the FXT system. They can install these boards in any available
universal board slot. Of course, any station boards or any other installed line boards reduce the number of lines
available for T1 service and thus reduces the number of T1 boards that installers can add to the system.
The installation must include the Synchronization card (DXOPT-SYN) on the auxiliary board whenever one or
more T1 boards is installed, and the FXT is receiving its timing signals from an external source. In installations
where the local FXT is supplying the clock signal for the far system, the local system does not require a
DXOPT-SYN card.
Installers can assign a system status button to a station and enable the system to report T1 transmission errors
via the T1 status log. Depending on how they program the system, the T1 status log either prints out on an
optional printer or is displayed on an optional video display terminal (VDT). A user can also view the T1 status
log from an LCD speakerphone by programming a system status button.
Also, installers can arrange the system to alert the system attendant whenever a major alarm alerting condition
occurs by activating an external, customer-supplied audible or visual alarm. The external alarm connects to one
of the relay jacks (J3 or J4) on the front of the CPU board. Installers must make sure the alarming device
complies with system voltage and power requirements. installers determine when a major alarm alerting
condition should occur by programming threshold values and corresponding time periods for each type of alarm
caused by a transmission error. Whenever the threshold value is reached within the programmed time period,
the selected relay on the CPU board is activated by the board’s circuits, which in turn, activates the external
alarm. The system attendant can turn the alarm off from any specified station by dialing a feature code.
6 – 88 General Description
GCA40–215 General Description