Nortel DMS-100 Series Maintenance Manual page 46

2-26 Star Remote System hardware
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297-8353-550 Standard 05.01 March 2001
card must be installed in slot positions 0 and 16 of the odd LSG to function
correctly.
Line card type C Meridian Digital Centrex (MDC) (NT6X21AA, AB, AC,
AD, BC, CA). Supports MDC-related electronic multiline telephone sets
and operator consoles.
Note: When an NT6X21AC line card is required, it must be installed at
least four slots away from the NT6X99AA IBERT line card.
The NT6X21AD line card provides a voice and signaling interface
between a 2-wire, analog subscriber line and one channel of the 4-wire,
32-channel, 2.56 Mb/s bit stream of the DMS-100 Family of the DMS
System. The card is in one slot in the line drawer of the Star Hub for use
with a proprietary phone (P-phone) telephone set that is connected to the
line card with an normal non-loaded (NL) pair of metallic conductors.
Simultaneous voice and extended signaling services are provided on the
same loop. The transmission bandwidth on the loop divides into two
frequency bands:
— voice channel, 300-3400Hz
— signaling channel 6-10kHz. Normal high-voltage signaling (ringing)
is replaced with low level signals.
The NT6X21AD is a single-line circuit line card that, with appropriate DIP
switch settings, is hardware backward compatible with the NT6X21AC
line card. The NT6X21AD provides improved features such as
— reduced messaging noise
— Dual in-line package (DIP) switch selectable balance impedance
— UDLC (universal digital loop carrier) improved operation
— DIP switch selectable (0 or -3.5dB) gain in the D/A (digital to analog)
direction
— DIP switch selectable short-loop/long-loop (slp/llp), signaling levels
The NT6X21AD card code, and maintenance and diagnostics on the new,
selectable signaling level, voice receive D/A level, and balance impedance