Verilink DIU 2130 (880-503297-001) Product Manual - Manual (Page 87)

DIU/DIM Details
Verilink 7-7
Figure 7-11 External Timing
DIU 2130 Clear Channel Operation Requirements
This section contains information on the Data Service Unit (DIU
2130) clear-channel operation requirements for 64 kbit/s
transmission.
On a normal T1 line, the following two requirements must be met
before transmitting the data onto the public network (as requested
by most tariffs):
1. Average ones density requirement—in general, 12.5% of
transmitted data must be ones, or the transmitted data must
have an average density of 12.5%.
2. Consecutive zeros requirement—transmitted data can have no
more than 15 zeros in a row.
Clear-Channel T1
Line
On a clear-channel T1 line, the transmitted data can contain
unrestricted zeros density (any number of ones and zeros) in any
combination.
A clear-channel T1 line is achieved by using B8ZS (Binary Eight
Zeros Substitution) before transmitting the data to the public
telephone network and decoding it at the other end. The NCC 2020
or TAC 2010 CSU does this encoding and decoding. The option is
set using Node Manager, Access Manager 2000, some other
management software, the Craft interface, or the master NCC/SCC
thumbwheel switch.
TT
ST
RT
T1 XMT Frequency
T1 RCV Frequency
DSU
(DCE)
Customer
Equipment
(DTE)
If the Far End is looped timed, then T1 XMT Frequency is = T1 RCV Frequency
If the Far End is not looped timed, then T1 XMT Frequency = T1 RCV Frequency