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    參數(shù)資料
    型號: MC33121
    廠商: Motorola, Inc.
    英文描述: LOW VOLTAGE SUBSCRIBER LOOP INTERFACE CIRCUIT
    中文描述: 低電壓用戶環(huán)路接口電路
    文件頁數(shù): 29/32頁
    文件大?。?/td> 570K
    代理商: MC33121
    MC33121
    MOTOROLA
    29
    Figure 51. Circuit Performance
    820
    //0.115
    μ
    F and 220
    System
    Figure 52. Return Loss Test Circuit
    for Figures 46 to 51
    80
    100
    60
    –0.2
    1.0 k
    10 k
    f, FREQUENCY (Hz)
    RL
    0
    T
    THR
    +0.2
    20
    40
    GTX
    GRX
    REFERENCE
    NETWORK
    IL
    R
    MC33121
    CIRCUIT
    (FIGURES 46,
    47 OR 48)
    Reference Network = RAC of Figures 46 to 48.
    Return Loss = 20 log
    VA– VB
    VA
    T
    VA
    VB
    VB
    GLOSSARY
    ATTENUATION
    — A decrease in magnitude of a commu-
    nication signal, usually expressed in dB.
    BALANCE NETWORK
    — That part of the SLIC circuit which
    provides transhybrid rejection.
    BANDWIDTH
    — The range of information carrying frequen-
    cies of a communication system.
    BATTERY
    — The voltage which provides the loop current,
    and in some cases powers the SLIC circuit. The name
    derives from the fact that COs have always used batteries, in
    conjunction with AC power, to provide this voltage.
    BATTERY FEED RESISTANCE
    — The equivalent Thevenin
    DC resistance of the SLIC circuit for supplying loop current.
    Traditionally it is 400
    .
    C–MESSAGE FILTER
    — A frequency weighting which eval-
    uates the effects of noise on a typical subscriber’s system.
    CENTRAL OFFICE
    — Abbreviated CO, it is a main tele-
    phone office, usually within a few miles of its subscribers,
    that houses switching gear for interconnection within its
    exchange area, and to the rest of the telephone system. A
    typical CO can handle up to 10,000 subscriber numbers.
    CODEC
    — Coder/Decoder — Interfacing between the SLIC
    and the digital switch, it converts the SLIC’s transmit signal to
    digital, and converts the digital receive signal to analog.
    dB
    — A power or voltage measurement unit, referred to
    another power or voltage. It is generally computed as:
    10
    log (P1/P2) for power measurements, and
    20
    log (V1/V2) for voltage measurements.
    dBm
    — An indication of signal power. 1.0 mW across 600
    ,
    or 0.775 Vrms, is defined as 0 dBm. Any other voltage level
    is converted to dBm by:
    dBm = 20
    log (Vrms/0.775), or
    dBm = [20
    log (Vrms)] + 2.22.
    dBmp
    — Indicates dBm measurement using a psophometric
    weighting filter.
    dBrn
    — Indicates a dBm measurement relative to 1.0 pW
    power level into 600
    . Generally used for noise measure-
    ments, 0 dBrn = – 90 dBm.
    dBrnC
    — Indicates a dBrn measurement using a C–
    message weighting filter.
    DTMF
    — Dual Tone Multifrequency. It is the “tone dialing”
    system based on outputting two non–harmonic related fre-
    quencies simultaneously to identify the number dialed. Eight
    frequencies have been assigned to the four rows and four
    columns of a keypad.
    FAULT
    — An incorrect condition where Tip is accidentally
    connected to the battery voltage, or Ring is connected to
    ground, or both. The most common fault is Ring to ground.
    FOUR WIRE CIRCUIT
    — The portion of a telephone, or cen-
    tral office, which operates on two pairs of wires. One pair is
    for the transmit path, and one pair is for the receive path.
    FULL DUPLEX
    — A transmission system which permits
    communication in both directions simultaneously. The stan-
    dard handset telephone system is full duplex.
    GAIN
    — The change in signal amplitude (increase or de-
    crease) after passing through an amplifier, or other circuit
    stage. Usually expressed in dB, an increase is a positive
    number, and a decrease is a negative number.
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