Cyclic Redundancy
Check (red LED)
When using the ESF format, the cyclic redundancy check (CRC) indicator lights
whenever there is a discrepancy in the check sum received for an incoming frame
from the originating system and the locally calculated check sum. This
discrepancy indicates a data error in the received frame. The CRC is enabled by
DIP switch SW2-4.
Slip (red LED)
This indicator is turned on whenever a frame slip is detected. This is caused by
the transmit clock not being synchronized with the receive clock.
Unlock (red LED)
The transmit frequency (1.544 Mhz) is not locked with the receive clock when
this indicator is lit.
B8ZS)/COFA (green LED)
This is a dual-purpose indicator. Depending on how you set DIP switch SW2-6,
this indicator reports either a change of frame alignment (COFA) at
re-synchronization time (default setting) or bipolar 8-zero substitution (B8ZS)
code words detected in the received data.
RLB, LLB, and
PAYL (red LEDs)
Whenever a loopback routine is active, either the remote loopback (RLB), local
loopback (LLB), or payback loopback (PAYL) mode (selected by DIP switches
SW2-7 and SW2-8) is indicated by the appropriate LED being lit.
PRI and SEC (green LEDs)
The PRI and SEC LEDs on the DXOPT-SYN card light to indicate where the
receive clock reference is originating from—the primary or secondary DXPT1
board location. When two or more DXPT1 boards are installed, you make the
primary and secondary assignments via jumpers on the the DXAUX board. If
only one DXPT1 board is installed, you can set the jumpers so that both LEDs
will light.
UNLOCKED (red LED)
When lit, the Unlocked LED indicates either the DXOPT-SYN card is defective
or the receive frequency is out of tolerance (1.544 Mhz
±
200 Hz).
MANUAL (red LED)
This LED, when lit, indicates that the manual mode has been selected via the
AUTO/MANUAL mode switch on the DXOPT-SYN card. When you select the
manual mode (normally for maintenance/troubleshooting ), you can select either
the primary or secondary timing reference by setting the PRI/SEC switch on the
DXOPT-SYN card. For normal operation, select the automatic mode. Do not
manually force the clock reference to primary or secondary if the appropriate
green LED is not lit. This will cause the VCO oscillator to default to its
minimum or maximum tolerance, and the T1 board(s) may not frequency-lock.
Installing The DXPT1 Line Board
IMI89–193
Installing The DXPT1 Line Board – 27