Toshiba Strata DK 280 Installation Manual page 633

4
Busy
LED (BSY)-Turns on when one or more
RDTU channels (lines) are in use. Also, when the
RDTU does not receive the far end 1.544 mbs
carrier signal, the RDTU will cause the BSY to be
on steady.
Alarms-are
features of the telephone network to
indicate a potentially serious problem. Example:
when monitoring a Tl network, if a Blue or Yellow
alarm is indicated, it can be concluded that there
is a cable fault or some other serious transmission
impairment.
H Frame Alarm (FALM)-This
LED will turn "ON"
steady if the RDTU has not achieved
synchronization or when the span cable is not
connected.
W Multi-Frame Alarm
(MFALM)-LEDs will turn
"ON" steady if the RDTU receives the 1.554 mbs
Tl carrier from the far end but has not achieved
Frame synchronization or when the span cable is
not connected. Also, if the RDTU is set for SF and
the far end is sending ESF (or vice versa), the
MFALM LED will be "ON" steady.
n
Red Alarm (FALM and
MFALM)-When FALM
and MFALM are both "ON" steady, a Red alarm
condition exists. This indicates that the RDTU
does not detect a proper carrier signal (1.544 mbs
Ti) on its receive pair and the RDTU is not
synchronized. When the Red alarm condition
exists, the RDTU should turn the BSY LED "ON"
steady and attempt to send a Yellow alarm signal
(RDTU YALM LED flashes) to the far end Tl
circuit.
H Yellow Alarm
(YALM)-When the far end
network or CPE Tl does not detect the RDTU
transmitted 1.544 mbs Tl carrier signal on its
receive pair the far end Tl will send a Yellow
alarm signal pattern to the RDTU-the RDTU
should turn on the YALM LED (the YALM will
repeat the signal it receives from the far end-
flashing or steady). If the RDTU does not receive
the far end carrier signal, the RDTU will send the
Yellow alarm signal to the far end and will cause
the BSY and YALM LEDs to flash.
n
Blue Alarm
(BALM)-The Blue alarm, also
known as the Alarm Indication Signal (AIS), is
detected by the RDTU. This signal is sent by the
Far End Network equipment to RDTU when it
loses the carrier from a Network 11 circuit (other
than RDTU). This signal assures that the RDTU
maintains synchronization when there is a
problem between two Network Nodes. The RDTU
BALM will also light if the far end sends a Blue
alarm signal during loop back. The RDTU will
send a Blue alarm signal when loop-back test is
being performed.
Synchronization LEDs (see Figure 11-l 2)
n
Primary Synchronization
(PSYNC) LED-If one
RDTU PCB is assigned as the Primary Timing Tl
PCB in Program *42, the PSYNC LED of this
RDTU PCB will flash when it is synchronized with
the far end Tl span line clock provider. If the
Primary RDTU is not synchronized with the clock
provider, the PSYNC LED will be ON steady. The
SSYNC LED of the Primary sync RDTU PCB
should always be OFF. The Primary sync RDTU
PCB synchronizes the RTCU (time-switch) to the
clock signal it receives from the Ti span circuit to
which it is connected. The RTCU then
synchronizes the DK280 PCM talk path (time-
switch) to the far end PCM talk path.
n
Secondary Synchronization (SSYNC)
LED-If
an RDTU PCB is assigned as the Secondary time
Ti PCB in Program *42, its SSYNC LED will be
ON steady (standby mode) when the DK280 is
synchronized to the Primary Tl clock provider. In
the event of a loss of Primary synchronization
(when 4 out of 12 consecutive frame timing bits
are in error) the DK280 will switch from
synchronizing to the Primary RDTU span line
clock to the span line clock connected RDTU
designated as the Secondary Timing Reference.
When the DK280 is synchronized to the
Secondary Reference RDTU, the PSYNC LED on
the Primary Reference RDTU will turn on steady
and the SSYNC LED on the Secondary Reference
RDTU will flash.
n
Run Free
(PSYNC/SSYNC)-If the RDTU PCB is
the clock provider to the Far-end Tl span circuit
both the PSYNC and SSYNC LEDs will always be
OFF.
11.5.4 RDTU Cable Installation
The RDTU PCB is shipped with a Toshiba NDTU
cable for connecting the RDTU PCB to a CSU. The
NDTU is a 30 ft. cable and is specially made to
conform with EIA specifications (see Figure 1 l-6). All
other cables required to connect the Ti span line to
the RDTU PCB are customer supplied and must
conform with EIA specification as described in Note 4
of Figure 11-6. Most all CSU manufacturers supply
January 1996
11-9