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fill-in signal unit (SS7) (FISU)

Fill-In Signal Unit (FISU) are pseudo data transmitted in SS7 networks as fill characters for error detection and synchronization.

They are intended to detect errors and problems on the transmission links before the connection is established. These fill signals are also transmitted when no other signals are present. They act as a kind of heartbeat and serve both end points for cyclic block checking(CRC).

Fill-in Signal Unit (FISU)

Fill-in Signal Unit (FISU)

The data frame of the FISU frame consists of 48 bits. Among them are check bits( CK) and data fields for the Length Indicator( LI), the Forward Sequence Number ( FSN), the Backward Sequence Number ( BSN), the Forward Indicator Bit ( FIB), the Backward Indicator Bit( BIB) and an 8-bit flag (F). The value for the Length Indicator (LI) is 0 for FISU.

Informations:
Englisch: fill-in signal unit (SS7) - FISU
Updated at: 23.06.2011
#Words: 128
Links: indium (In), data, signalling system no 7 (SS7), error, synchronization (SYN)
Translations: DE
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