參數(shù)資料
型號： L9311
英文描述： Line Interface and Line Access Circuit Full-Feature SLIC with High Longitudinal Balance, Ringing Relay,and GR-909 Test Access
中文描述： 線路接口和線路接入電路全功能用戶接口高縱向平衡，振鈴繼電器，和GR - 909測試訪問
文件頁數(shù)： 40/50頁
文件大?。?/td> 852K
代理商： L9311
Data Sheet
July 2001
Ringing Relay, and GR-909 Test Access
L9311 Full-Feature SLIC with High Longitudinal Balance,
40
Agere Systems Inc.
ac Applications
ac Parameters
There are four key ac design parameters.
Termination
impedance
is the impedance looking into the 2-wire
port of the line card. It is set to match the impedance of
the telephone loop in order to minimize echo return to
the telephone set.
Transmit gain
is measured from the
2-wire port to the PCM highway, while
receive gain
is
done from the PCM highway to the transmit port.
Transmit and receive gains may be specified in terms
of an actual gain, or in terms of a transmission level
point (TLP), that is the actual ac transmission level in
dBm. Finally, the
hybrid balance
network cancels the
unwanted amount of the receive signal that appears at
the transmit port.
Codec Types
At this point in the design, the codec needs to be
selected. The interface network between the SLIC and
codec can then be designed. Below is a brief codec
feature summary.
First-Generation Codecs.
These perform the basic
filtering, A/D (transmit), D/A (receive), and
μ
-law/A-law
companding. They all have an op amp in front of the
A/D converter for transmit gain setting and hybrid bal-
ance (cancellation at the summing node). Depending
on the type, some have differential analog input stages,
differential analog output stages, +5 V only or
±
5 V
operation, and
μ
-law/A-law selectability. These are
available in single and quad designs. This type of
codec requires continuous time analog filtering via
external resistor/capacitor networks to set the ac
design parameters. An example of this type of codec is
the Agere T7504 quad 5 V only codec.
This type of codec tends to be the most economical in
terms of piece part price, but tends to require more
external components than a third-generation codec.
Further, ac parameters are fixed by the external R/C
network so software control of ac parameters is diffi-
cult.
Third-Generation Codecs.
This class of devices
includes all ac parameters set digitally under micropro-
cessor control. Depending on the device, it may or may
not have data control latches. Additional functionality
sometimes offered includes tone plant generation and
reception, PPM generation, test algorithms, and echo
cancellation. Again, this type of codec may be +5 V
only or
±
5 V operation, single quad or 16-channel, and
μ
-law/A-law or 16-bit linear coding selectable. Exam-
ples of this type of codec are the Agere T8536/7 (5 V
only, quad, standard features), T8533/4 (5 V only, quad
with echo cancellation), and the T8531/36 (5 V only 16-
channel with self-test).
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相關(guān)代理商/技術(shù)參數(shù)
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