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Page 160 of 894 NT1R20 Off-Premise Station Analog Line card
553-3001-211 Standard 2.00 September 2004
Line interface units
The NT1R20 OPS analog line card contains eight independently configurable
interface units. Relays are provided in each unit to apply ringing onto the line.
Signal detection circuits monitor on-hook/off-hook signaling. Two codecs
are provided for performing Analog/Digital (A/D) and Digital/Analog (D/A)
conversion of analog voiceband signals to digital PCM signals.
Each codec supports four interface units and contains switchable pads for
control of transmission loss on a per unit basis. The following features are
common to all units on the card:
• OPS or ONS service configurable on a per unit basis
• terminating impedance (600 or 900 ohms) selectable on a per unit basis
• standard or complex balance impedance (600 or 900 ohms, 3COM1 or
3COM2) selectable on a per unit basis
• loopback of PCM signals over DS-30X network loop for diagnostic
purposes
Signaling and control
This portion of the card provides circuits that establish, supervise, and take
down call connections. These circuits work with the CPU to operate 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.
Card control functions
Control functions are provided by a microcontroller, a card LAN interface,
and signaling and control circuits on the NT1R20 OPS analog line card.
Microcontroller
The NT1R20 OPS analog line card contains a microcontroller that controls
the internal operation of the card and the serial card LAN link to the controller
card. The microcontroller controls the following:
• reporting to the CPU through the card LAN link:
— card identification (card type, vintage, and serial number)