
Overview
Page 39 of 906
Circuit Card
Description and Installation
Coder/Decoder circuit
The Coder/Decoder (CODEC) performs Analog to Digital (A/D) and Digital
to Analog (D/A) conversion of the line analog voiceband signal to and from
a digital PCM signal. This signal can be coded and decoded using either the
A-Law or the µ-Law companding algorithm.
On some analog line cards, the decoding algorithm depends of the type of
CODEC installed when the board is built. On others, it is an option selected
using a software overlay.
Variable gain filters
Audio signals received from the analog phone line are passed through a
low-pass A/D monolithic filter that limits the frequency spread of the input
signal to a nominal 200 to 3400 Hz bandwidth. The audio signal is then
applied to the input of the CODEC. Audio signals coming from the CODEC
are passed through a low-pass A/D monolithic filter that integrates the
amplitude modulated pulses coming from the CODEC, and then filters and
amplifies the result. On some of the line cards, the gain of these filters can be
programmed by the system controller. This allows the system to make up for
line losses according to the loss plan.
Balancing network
Depending on the card type, the balancing network provides a 600 ¾, 900 ¾,
3COM or 3CM2 impedance matching network. It also converts the 2-wire
transmission path (tip and ring) to a 4-wire transmission path (Rx/ground and
Tx/ground). The balancing network is usually a transformer/analog (hybrid)
circuit combination, but can also be a monolithic Subscriber Line Interface
Circuit (SLIC) on the newer line cards.
Line interface and foreign voltage protection
The line interface unit connects the balancing network to the telephone tip
and ring pairs. The off-premise line card (NT1R20) has circuitry that protects
the line card from foreign voltage surges caused by accidental power line
connections and lightning surges. This protection is necessary if the
telephone line leaves the building where the switch is installed.
The line interface unit has a relay that applies the ringing voltage onto the
phone line. See Figure 4 on
page 38
. The RSYNC signal from the 20 Hz
Содержание Circuit Card
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Страница 4: ...Page 4 of 906 Revision history 553 3001 211 Standard 3 00 August 2005...
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Страница 78: ...Page 78 of 906 Overview 553 3001 211 Standard 3 00 August 2005...
Страница 100: ...Page 100 of 906 Acceptance tests 553 3001 211 Standard 3 00 August 2005...
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Страница 192: ...Page 192 of 906 NT4N39AA CP Pentium IV Card 553 3001 211 Standard 3 00 August 2005...
Страница 248: ...Page 248 of 906 NT5D11 and NT5D14 Lineside T1 Interface cards 553 3001 211 Standard 3 00 August 2005...
Страница 378: ...Page 378 of 906 NT5K21 XMFC MFE card 553 3001 211 Standard 3 00 August 2005...
Страница 384: ...Page 384 of 906 NT6D70 SILC Line card 553 3001 211 Standard 3 00 August 2005...
Страница 388: ...Page 388 of 906 NT6D71 UILC Line card 553 3001 211 Standard 3 00 August 2005...
Страница 533: ...NT8D02 and NTDK16 Digital Line cards Page 533 of 906 Circuit Card Description and Installation Figure 106 NTDK16 DLC...
Страница 544: ...Page 544 of 906 NT8D02 and NTDK16 Digital Line cards 553 3001 211 Standard 3 00 August 2005...
Страница 546: ...Page 546 of 906 NT8D03 Analog Line card 553 3001 211 Standard 3 00 August 2005...
Страница 564: ...Page 564 of 906 NT8D09 Analog Message Waiting Line card 553 3001 211 Standard 3 00 August 2005...
Страница 626: ...Page 626 of 906 NT8D14 Universal Trunk card 553 3001 211 Standard 3 00 August 2005...
Страница 680: ...Page 680 of 906 NT8D41AA Serial Data Interface Paddle Board 553 3001 211 Standard 3 00 August 2005...
Страница 694: ...Page 694 of 906 NT8D41BA Quad Serial Data Interface Paddle Board 553 3001 211 Standard 3 00 August 2005...
Страница 720: ...Page 720 of 906 NTAK09 1 5 Mb DTI PRI card 553 3001 211 Standard 3 00 August 2005...
Страница 734: ...Page 734 of 906 NTAK10 2 0 Mb DTI card 553 3001 211 Standard 3 00 August 2005...
Страница 744: ...Page 744 of 906 NTAK20 Clock Controller daughterboard 553 3001 211 Standard 3 00 August 2005...
Страница 762: ...Page 762 of 906 NTAK79 2 0 Mb PRI card 553 3001 211 Standard 3 00 August 2005...
Страница 768: ...Page 768 of 906 NTAK93 D channel Handler Interface daughterboard 553 3001 211 Standard 3 00 August 2005...
Страница 772: ...Page 772 of 906 NTBK22 MISP card 553 3001 211 Standard 3 00 August 2005...
Страница 844: ...Page 844 of 906 NTVQ01xx Media Card 553 3001 211 Standard 3 00 August 2005...
Страница 850: ...Page 850 of 906 NTVQ55AA ITG Pentium card 553 3001 211 Standard 3 00 August 2005...
Страница 884: ...Page 884 of 906 QPC841 Quad Serial Data Interface card 553 3001 211 Standard 3 00 August 2005...
Страница 906: ...Page 906 of 906 Appendix A LAPB Data Link Control protocol 553 3001 211 Standard 3 00 August 2005...
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