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21.3 E1 Frame Words
This function requires the E1 signal to be framed. The NFAS word is used to carry information about the status of the link and to
provide control signals for primary rate multiplexers. Sa bits are often used to transmit the clock quality level (QL) SSM
information. Use can select the one of the RX Sa bits to be decoded as SSM.
Bit 1: Reserved for International use (M is used to transmit the CRC multiframe signal in PCM30C and PCM31C)
Bit 2: Set to “1” to prevent simulation of FAS
Bit 3: A shows the remote alarm indication
Bits 4 to 8: Sa4 to Sa8 are spare bits, often used for SSM QL.
Tx: Bits Sa4 to Sa8 are used to send optional network messages. The Sa bits should be set to “1” when they are not used or
when links cross International borders. To edit a Sa bit sequence, tap on the desired numeric field and enter the new 8-bit
sequence using the pop-up keypad. For a list of SSM QL codes refer to ITU-T G.704 Section 2.3.4
Rx: Bit Sa4 can be used as a message based data link for operations, maintenance and performance monitoring.
E1 Frame Words - Rx SSM bits E1 Frame Words - Tx
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21.4 Round Trip Delay
TX130M+_e-manual_D07-00-051P_RevD00
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