CRC-4 (Cyclic Redundancy Check 4)
CRC-4 (Cyclic Redundancy Check 4) is a form of cyclic
redundancy checking (a method of checking for errors in transmitted data) that is used on E-1
trunk
lines. CRC-4 is structured in a multiframe consisting of 16 frames numbered 0 to 15. The CRC-4
multiframe is then divided into two eight frame
Sub-Multiframes (SMF) called SMF I and SMF II. Each SMF contains four CRC-4 bits designated C1, C2,
C3, and C4. Through multiplication and division processes, the CRC-4 bits sent in each SMF are
compared to each other and if they match, the frame is considered error free. Bit 1 is used for the
CRC-4 bits.
CRC-4 support is required for all network switches in Europe. However, some older switches
including private branch exchanges (PBXs) do not support CRC-4.
Contributor(s): Neil Stone-Wigg
This was last updated in April 2007
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