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interface, as per the requirement specified in the applicable standard (DSX-1 for DSU
network interface, ANSI T1.403 for CSU network interface). See Appendix C for more
details about CSU and DSU network interfaces.
CRC6 Usage
The F-bits in an ESF multiframe (see Superframe method above) provide Cyclic Redundancy
Check 6 (CRC6) information. These bits are the result of a certain calculation performed on
all the bits of the previous multiframe (24 frames). CRC6 bits may be used by the receiving
equipment to determine correct reception of all bits sent to it. There are two common CRC6
procedures:
• In accordance with the ANSI, AT&T and ITU-T standards
• In accordance with the Japanese JT-704 standard.
Set CRC Usage in accordance with the CRC6 procedure used by the connected end
equipment.
Bit 7 Zero Suppression
When using AMI line code, the occurrence of too many successive zeros should be avoided
to ensure accurate reconstruction of the data. Some devices use a method known as zero
suppression. This method forces bit 7 of each 8-bit channel to 1 if all the bits in the original
channel are zero.If the connected end equipment uses the bit 7 zero suppression method, this
parameter should be set to 1 (Force bit 7 zero suppression). Otherwise (see also Pulse Density
Enforcer below) it should be set to 0 (no suppression). If the line code used is B8ZS, it must
be set to 0 (no suppression). When transmitting data (non-voice) it must be set to 0 (no
suppression) unless the data is preconditioned not to send “all zero” bytes.
Pulse Density Enforcer
When using AMI line code, the occurrence of too many successive zeros should be avoided
to ensure accurate reconstruction of the data. Some devices use a method known as Pulse
Density Enforcer according to ANSI T1.403. This method checks the number of ones, and
upon detecting too many successive zeros it forces certain bit(s) to one. If the connected end
equipment uses the Pulse Density Enforcer method, this parameter should be set to 1 (Enable
Pulse Density Enforcer). Otherwise (see Bit 7 Zero Suppression above) it should be set to 0
(Disable Pulse Density Enforcer). If the line code used is B8ZS, it must be set to 0 (Disable
Pulse Density Enforcer). When transmitting data (non-voice) it must be set to 0 (Disable
Pulse Density Enforcer) unless the data is preconditioned not to send “all zero” bytes.
Echo Canceler
Set this parameters in accordance with the echo cancellation disabling method used by the
end equipment(see also appendix C).