
PEB 80900
Part II
’
IEC-T
’
: Functional Description
Data Sheet
107
2001-04-02
6.7.1.2
Switching Loop 2 in the
NTC-T AM with IEC-T Functionality Selected
in
NT-PABX and TE Modes
The loop 2 can be closed in the NTC-T AM with IEC-T functionality selected in NT-PABX,
NT-PABX-BURST and NT-TE modes. With an internal switch, the user data on DOUT
(B+B+D+T) is directly fed back into DIN. The control input (MONITOR and C/I channel)
is still read from the IOM
interface. Although loop 2 is closed by command from the
exchange, the NTC-T AM with IEC-T functionality selected can still be deactivated by
RES and SSP C/I channel commands from the layer 2 device.
The loop 2 is under remote control from the exchange, identical to the loop 2 switched
in the SBC.
In the NT-PABX and NT-TE modes, loop 2 can
’
t be closed while the local loop 3 is
activated. The activation of loop 3 leads to the deactivation of an activated loop 2.
6.7.1.3
Remote Control of Loop 4 and Loop 2 by the
NTC-T AM with IEC-
T Functionality Selected
These remote loops are controlled by the exchange via C/I channel of the NTC-T AM
with IEC-T functionality selected (LT-mode). The command for closing loop 4 or loop 2
is transmitted from the exchange on the Uk0 interface in the 1 kbaud M channel (position
85 downstream in the Uk0 frame from LT to NT).
To command the NTC-T AM with IEC-T functionality selected in LT-repeater mode to
close loop 4, the NTC-T AM with IEC-T functionality selected in NT-repeater mode has
to find alternating plus and zero polarity within 8 subsequent frames in the M channel
(+0+0+0+0...).
To command the SBC in the NT to close loop 2, the NTC-T AM with IEC-T functionality
selected in the NT has to find continuous plus polarity within 8 subsequent frames in the
M channel (++++++++...). The same code has to be found by the NTC-T AM with IEC-T
functionality selected in NT-PABX or NT-TE mode to close loop 2 itself.
Note: The NTC-T AM with IEC-T functionality selected in NT mode does not close loop2
itself.
To open closed loops, the NTC-T AM with IEC-T functionality selected in NT, NT-RP,
NT-PABX, NT-TE mode has to find continuous zero polarity within 8 subsequent frames
in the M channel (00000000...) or at deactivation. During normal transmission without
loops, the M symbol is set to zero (or minus see
Chapter 6.7.3
“
Transparent
Maintenance Channel
”
on Page 109
).
The NT-RP, when detecting positive M symbols, does not close loop 2, but hands them
over to LT-RP via the IOM
interface with a high in the E bit of 8 subsequent IOM
frames. Negative or zero M symbols cause 8 low E bits.