User manual

Product Description

Framing Modes

2-10 July 2004 Wide Bank 28 DS3 - Release 2.4

X-Bits - Error Message from Far-End to Near-End

The X-bits, located in the first bit position of both M-subframe 1 and M-subframe 2 (see Figure

2-2), are both set to zero (0) if a Loss-of Signal (LOS), Out-of-Frame (OOF), or Alarm

Indication Signal (AIS) is detected at the far-end during any one-second interval. This signal is

transmitted to the near-end for one second, then the X-bits return to their normal condition (both

ones). X-bit states of 01 or 10 are abnormal and are ignored by the near-end.

Application Identification Channel (AIC) Bit

The first C-bit in M-subframe 1, the AIC bit, indicates whether the far-end equipment is set for

C-bit parity framing (1), or M23 framing (random 1s and 0s). See Figure 2-3.

Reserved Network Application (Na) bit

This bit is always a one (1). See Figure 2-3.

Figure 2-3 Subframe 1 C-bits

679

Bits

X 679 679 679 679 679 679P P MO M1 MO

M Frame (4760 bits)

Subframe

1X 84 F1 84 84 84 84 84 84

AIC

FEA

F1 S1 83

680

Bits

M Subframe No. 1

Indicates Framing

Mode of the Equipment

(1 = C-bit parity)

Reserved Network

Application Bit

Sends Alarm/Status Information from

Far-End Terminal back to Near-End

Terminal