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INTRODUCTION
1-13
end, one framing bit is inserted in each succeeding 193rd bit-position of the DS1 signal. The receive
end uses the framing pattern to synchronize the end of one 24-channel block and the beginning of the
next, to identify the channels that contain embedded signaling information, and to detect errors.
NOTE: This 4K-bps facility data link is designed to maintain and supervise a DS1 facility.
However, this link is used by a System 75 and System 85 DS1s only for transmitting yellow
alarms.
Each 24-frame entity, spanning one ESF cycle, is called the ESF superframe. Figure 1-6, DS1 Signal,
Framing Format, and ESF Superframe (24 Frames), shows an ESF superframe.
NOTE:
For RBS, frames 6, 12, 18, and 24 carry signaling information.
Figure 1-6. DS1 Signal, Framing Format, and ESF Superframe (24 Frames)