User manual

Wide Bank 28 DS3 - Release 2.4 July 2004 2-11
Product Description
Framing Modes
Far End Alarm (FEA) Bit
The FEA bit is used for two purposes: (1) as a far-end channel to send alarm and status
information from the far-end to the near-end, and (2) to initiate from the near-end, DS3 and low-
speed loopbacks at the far end terminal. A 16-bit code is transmitted serially over this one-bit
channel, least-significant (right-end) bit first, to indicate one of eleven conditions. The format
of the 16-bit code is: 0XXXXXX0 11111111 (where X can be a 1 or a 0).
Table 2-1 FEA Bit Far-End Alarm and Status Channel Codes
CP Bits
The three C-bits of Subframe 3, called the CP bits, are used to transport DS3 parity information.
At the DS3 transmit location, they are set to the same value as the P-bits of Subframes 3 and 4.
See Figure 2-4 and Figure 2-5.
P-Bits
The first bit of both Subframes 3 and 4 are called P-bits. They are used as parity indication bits
for information bits, and are monitored for indications of DS3 signal errors. See Figure 2-4 and
Figure 2-5.
Far-End Block Error (FEBE) Bits
If an incoming path error (framing error or parity error) is detected at the receiving side, the
three FEBE bits are set to any combination of 1s and 0s except 111, and sent to the far-end
terminal. A setting of 111 means there are no framing or parity errors. See Figure 2-5.
Alarm or Status Condition 16-Bit Code
1 DS3 equipment failure (service-affecting) 00110010 11111111
2 DS3 LOS 00011100 11111111
3 DS3 out-of-frame 00000000 11111111
4 DS3 AIS received 00101100 11111111
5 DS3 IDLE received 00110100 11111111
6 DS3 equipment failure (not service-affecting) 00011110 11111111
7 Common equipment failure (not service-affecting) 00111010 11111111
8 Multiple LS LOS 00101010 11111111
9 LS equipment failure (service-affecting) 00001010 11111111
10 Single LS LOS 00111100 11111111
11 LS equipment failure (not service-affecting) 00000110 11111111