ADTRAN T1-FT1 - Manual (Page 29)

Chapter 1. Introduction
61200060L1-1 TSU User Manual 1-13
DTE Interface Loopbacks
The Nx56k/64k serial interface offers a DTE loopback. See
Figure 1-8.
DTE Loopback : loops all data from the DTE back towards
the DTE. This loopback may be initiated by the DTE asserting
the Local Loopback (LL) input on the connector or by using
front panel or T-WATCH commands. The DTE (or external
test equipment) must provide any test pattern in order to
check the DTE interface.
Figure 1-8. DTE Interface Loopback
Pattern Generation
The TSU offers four available test patterns, All Ones, 3:24,
and 511 and 1:8.
All Ones
Need definition
3 in 24
The 3:24 is a stress pattern which places the maximum
number of 0s in the transmitted data. This is always done
over all DS0s. This pattern is used in conjunction with
external test equipment to determine if the T1 line is
preforming acceptably under a stress condition.
TSU
to DTE
T1
DTE
Loopback
Nx56/64
Interface
Nx56/64 to
network control
circuit
Network Interface
(NI)