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.
Since the DXP Plus supports a maximum of 240 lines, and each T1 board handles up to 24 channels,
installers can place up to 10 T1 boards in the DXP Plus system. They can install these 10 boards in any
available universal board slot in the main and expansion cabinets. Of course, any other installed line
boards, such as loop start, DID or multipurpose, 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 Syncronization card (DXOPT-SYN) on the Services board whenever
one or more T1 boards is installed, and the DXP Plus is receiving its timing signals from an external
source. In installations where the local DXP Plus is supplying the clock signal for the far system, the local
system does not require a DXOPT-SYN card.
Programmers 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, programmers 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 DXCPU board. Installers must make sure
the alarming device complies with system voltage and power requirements. Programmers 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 DXCPU 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.
Pad Level—Transmit, Receive
(Gain And Attenuation Settings For Line Transmit And Receive)
This feature enhances the T1–E1 digital carrier transmission option, the pad level programming feature
adjusts voice levels for both the transmit and receive circuits in the individual channels.
The choices include: Gain 2, Gain 1, Nominal, Loss 1, Loss 2, Loss 3, Loss 4, and Loss 5. These settings
provide an appro6 to -15 dB range of choices. Starting at the Nominal setting, each gain level
represents an approximate 3 dB amplification of the signal level from the previous setting, and each loss
level represents an approximate 3 dB attenuation of the signal level from the previous setting. Because
digital transmission does not lose volume level as readily as analog transmission does, it is likely that the
receive level may be noticeably higher when using the E1 option. Therefore, you may need to select a low
setting such as Loss 2 for the voice level receive parameter when programming this feature for E1 lines
that are being used exclusively for voice transmission. Further, if you choose a setting to increase the
receive gain, you should carefully examine speakerphone operation. It is possible to select a receive gain
that will, under certain conditions, interfere with proper speakerphone operation.
DXP Plus General Description
GCA40–130
Understanding The Features – 107
