psf21911 ETC-unknow, psf21911 Datasheet - Page 76

• Manufacturer Part Number: psf21911
• Description: Isdn Echocancellation Circuit Terminal Applications Iec-q
• Manufacturer: ETC-unknow

Semiconductor Group
2.5.9
Test loop-backs are specified by the national PTTs in order to facilitate the location of
defect systems. Four different loop-backs are defined. The position of each loop-back is
illustrated in figure 23.
Figure 23 Test Loop-Backs Supported by the IEC-Q TE
Loop-backs #1, #1A and #2 are controlled by the exchange. Loop-backs #3 is controlled
by the terminal. All loop-back types are transparent. This means all bits that are looped
back will also be passed onwards in the normal manner.
2.5.9.1
Normally loop-back #2 is controlled from the exchange via the EOC commands LBBD,
LB1 and LB2. In EOC auto mode the EOC commands are recognized and executed
automatically (see page 51). The single channel loop-backs (LB1, LB2) are closed in the
U-transceiver itself whereas the complete loop-back (LBBD) is closed in a connected S-
transceiver.
All loop-back functions are latched. This allows channel B1 and channel B2 to be looped
back simultaneously. All loop-backs are opened when the EOC command RTN is sent
by the LT.
S-Bus
Layer 1 Loop-Backs
Loop-Back (No. 2)
Loop 2
SBCX
ICC
ICC
PBX or TE
IOM
IOM
NT
R
R
IEC-Q TE
IEC-Q TE
IEC-Q TE
Loop
Loop 2
Loop
3
2
U
Loop
IEC-Q
76
Repeater (optional)
1a
IOM
R
IEC-Q
U
Exchange
IEC-Q
Loop 1
U-Transceiver
IOM
PSB 21911
PSF 21911
ITD10198
R
11.97