Verilink Access Manager 2000 (896-502037-001) Product Manual - Manual (Page 352)

A-20 Access Manager 2000 Manual
Yellow Alarm A Yellow Alarm is the alarm a receiving channel bank or multiplexer
sends to the other end of the circuit when it detects a loss of signal or
loss of frame. There is a 2- to 3-second integration period upon
detection of loss of signal or loss of frame before a yellow alarm is sent
to the far-end equipment. This condition is also referred to as a remote
alarm or remote alarm indication:
In the Superframe format, a yellow alarm consists of Bit 2 of all 24
channels set to zero.
In ESF format, the yellow alarm is a repeating pattern of eight ONEs
followed by eight ZEROs transmitted over the ESF Data Link.
Yellow Alarm
Transcoding When a DS1 signal undergoes framing format conversion from SF (D4)
to ESF, or ESF to SF, an existing yellow alarm must be transcoded to
the new format so that the alarm can be detected by the network or
DTE equipment. An integration time is used before transcoding occurs
to allow for data that merely looks like yellow alarm (in the SF mode),
and to allow for detection of a yellow alarm in the presence of errors.
For SF, the detection and clear time is 400 +/- 1 millisecond. For ESF,
this time is 63 to 66 milliseconds.
Zero Code
Suppression The insertion of a “one” bit to prevent the transmission of eight or more
consecutive “zero” bits; used primarily with T1 and related digital
circuits.
Term Definition