Patent attributes
An alarm indication translation mechanism in a digital access and cross-connect system monitors all incoming tributary DS1 streams for the presence of an alarm indication. Whenever an alarm indication is detected in a fractional tributary DS1 data stream, all DS0 bytes within the T1 stream containing that tributary DS1 data stream include the detected alarm indication. For a Yellow alarm, this means that for the case of D4 superframe format (SF), the second most significant bit of each of the twenty-four bytes of a T1 frame containing at least one fractional DS1 carrying alarm information is set to a ‘0’, irrespective of whether the bytes are valid DS0s or idle bytes. For extended superframe format (ESF), Yellow alarm is transmitted by sending a repetitive sixteen bit pattern consisting of eight marks or ‘1’s, followed by eight spaces or ‘0’s in the data link.
