Nortel NT1R20, Description

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NT1R20 Off-Premise Station Analog Line Card Page 59 of 290
Line cards Description
Card LAN interface
Maintenance data is exchanged with the Common Equipment CPU over a
dedicated asynchronous serial network called the Card LAN link. The Card
LAN link is described in the section “Intelligent peripheral equipment” on
page 18.
The OPS analog line card has the capability of providing an interrupted dial
tone to indicate that a message is waiting or that call forwarding is enabled.
The line card (optionally) receives messages stating that these conditions
exist over the Card LAN Interface and interrupts the dial tone when either of
these conditions are detected.
Signaling and control
The signaling and control portion of the card provides circuits that establish,
supervise, and take down call connections. These circuits work with the
system CPU to operate the line interface circuits during calls. The circuits
receive outgoing call signaling messages from the CPU and return incoming
call status information over the DS-30X network loop.
Circuit power
The +8.5 V dc input is regulated down to +5 V dc for use by the digital logic
circuits. All other power to the card is used by the line interface circuits. The
±15.0 V dc inputs to the card are used to power the analog circuits. The
+5 V dc from the module power supply is used for the analog hybrid. The
–48.0 V dc input is for telephone set battery. Ringing power for telephone sets
is 86 Vrms ac at 20 Hz on –48 V dc. The Rsync signal is used to switch the
20 Hz ringing on and off at the zero cross-over point to lengthen the life of
the switching circuits.