CH1837A/8A Data Access Arrangement Module
V.34bis High Speed DAA Module
INTRODUCTION
DESCRIPTION OF FUNCTIONAL BLOCKS
The Cermetek CH1837A Data Access Arrangement
AND DISCUSSION OF BASIC OPERATIONS
(DAA)
is
designed
to
meet
the
performance
Figure 1 contains a functional block drawing of the
requirements of 33.6Kbps modems, such as V.34bis,
CH1837A. Each CH1837A product consists of:
for embedded applications. The CH1837A meets or
1) Isolation barrier.
exceeds the requirements for V.34 and can be used in
2) Off-Hook Switch/Ring Detect circuit.
lower speed applications as well. The isolation voltage
3) PSTN Line Surge and High Voltage Protection
and surge protection meets, as a minimum, North
circuitry.
American UL60950/3 edition (USA) and CSA C22.2
rd
4) 2-to-4 Wire Conversion circuit.
950 (Canada) requirements. Further, the CH1837A will
meet FCC Part 68 (TIA/EIA/IS-968) and is Canadian
V cc
VND
DOT CSA CS-03 Part I approvable when properly
designed in.
SURGE AND
TIP
The CH1837A is compatible with all popular V.34bis
ISOLATION
PROTECTION
modem/fax chip sets.
Application examples are
CIRCUITRY
RING
included in this datasheet.
The CH1837A offers a
Quick-to-Market DAA solution for high performance
T1
T2
XMIT+
modem designs.
HYBRID
OFF HOOK
XMIT-
2W/4W
SWITCH
The CH1837A is exceptionally well suited for voice-
RCV
CONVERTER
RING DET.
over-data (VoIP) and other internet-based telephony
and data communication applications.
RI
OFFHK
For those applications not requiring a two to four wire
hybrid converter circuit, the CH1838A provides all the
features of the CH1837A (except the hybrid converter)
Figure 1. Function Block Diagram of CH1837A.
while offering some cost savings.
Note that the
CH1838A is a special order product only.
Consult
Figure 2 contains a functional block drawing of the
Cermetek for availability and delivery.
CH1838A. Each CH1838A product consists of:
1) Isolation Barrier.
2) Off-hook Switch/Ring Detect circuit.
FEATURES
3) PSTN Line surge and High Voltage Protection
  • Low Profile.
  • Circuitry.
  • Complete DAA function.
  • Figure 2. Function Block Diagram of CH1838A.
  • Compatible with most popular V.34bis modem chip
  • sets.
    V cc
    VND
  • Ring detection circuitry included.
  • Built-in 2-wire to 4-wire conversion circuitry
  • SURGE AND
    TIP
    (CH1837A only).
    ISOLATION
    PROTECTION
  • UL60950/3 rd
  • edition Listed and CSA C22.2 950
    CIRCUITRY
    RING
    Compliant. See UL File E104957.
  • 1500 VAC RMS Isolation.
  • T2
    OFF HOOK
  • 2122V peak surge protection.
  • N/C
    N/C
    SWITCH
  • +5V low power operation.
  • RING DET.
    T1
  • Differential transmission, VoIP applications.
  • RI
  • Compatible with V.34bis, V.32bis, V.32, V.22bis,
  • and V.22.
    OFFHK
  • FCC Part 68 (USA) and DOT CSA CS-03 Part I
  • (Canada) Approvable.
    2004 Cermetek Microelectronics, Inc.
    Page 1
    Document No. 607-0014 Revision C3 (02/04)
    Cermetek Microelectronics, Inc.
    CH1837A/8A Data Access Arrangement Module
    Ring Detection. To announce an incoming call, the
    OFFHK Input:
    Active HIGH
    telephone company’s central office (CO) applies an
    OFFHK active Current: 5mA
    AC ringing signal to the PSTN line. The CH1837A/8A
    is designed to detect this signal. The CH1837A/8A
    uses the AC ring signal to produce a square wave
    pulse train output at the CH1837A/8A RI pin. This
    pulse train is the same frequency as the incoming AC
    ring signal and is typically 20 Hz. Figure 3 shows
    external filtering which may be employed to provide an
    envelope indication of the ring signal using the
    CH1837A/8A RI output. The ring detection circuit in
    the CH1837A/8A family is designed to deter false
    indications caused by pulse dialing or noise on the
    PSTN line.
    Additionally, the RI output of the CH1837A/8A is diode
    protected thereby allowing an external pull-up resistor
    (R>100k ohms) to +5V to be utilized to activate the
    ring detection circuit when the CH1837A/8A is not
    connected to power. This can be handy for designs in
    which power consumption is of concern.
    When
    Figure 4. Low Power Ring Detection Circuit.
    circuited in this manner, there is virtually no current
    draw until a ring signal is present. Refer to Figure 4.
    2-Wire to 4-Wire Hybrid Converter (CH1837A only).
    This circuit block performs two functions:
    1. It applies the XMIT signal to the PSTN line, and
    RI Output:
    Opt coupler, 30K pull-up, Active
    2. It subtracts the XMIT signal from the total signal
    LOW
    present on the PSTN line thereby deriving the
    Square wave 15-68HZ (TIP. 20Hz)
    RCV signal.
    Sensitivity: 38Vrms across TIP and RING
    The accuracy of the RCV signal derivation depends on
    how closely the impedance of the PSTN line matches
    an ideal 600 Ohms. Generally, a small amount of the
    XMIT signal will appear at RCV due to the non-ideal
    nature of the PSTN line impedance. The ratio of the
    applied XMIT signal to the received XMIT signal is
    called Trans-Hybrid Rejection, or Trans-Hybrid Loss.
    PSTN Line Isolation and Surge/Peak Voltage
    Protection. The Public Switched Telephone Network
    (PSTN) line isolation barrier circuitry provides isolation
    and the required surge and high voltage protection.
    This circuitry effectively isolates the user’s equipment
    from both the PSTN line and the CO.
    The
    CH1837A/8A has been designed to meet both FCC
    Part 68 (USA) and DOT CSA CS-03 Part I (Canada)
    isolation and surge requirements when circuited as
    Figure 3. Typical Application.
    indicated in Figure 5.
    Among the more critical
    parameters, the PSTN isolation barrier will provide at
    Hook Switch Control.
    least 1500VAC RMS isolation and 2122V peak surge
    protection.
    The CH1837A/8A is also UL60950/3
    rd
    The OFFHK input is used to toggle the CH1837A/8A
    from On-Hook to Off-Hook and back to On-Hook.
    edition listed and meets CSA C222-950 test conditions
    when connected as indicated in Figure 5.
    When the OFFHK input is TTL Low, the CH1837A/8A
    is On-Hook. The On-Hook state indicates to the CO
    that the CH1837A/8A is ready to receive calls.
    TRANSMIT SIGNALS
    The CH1837A/8A does not attenuate the transmit
    When the OFFHK input is TTL High, the CH1837A/8A
    signal before it applies the signal across tip and ring.
    is Off-Hook. The Off-Hook state indicates to the CO
    Therefore, a transmit signal of –9dBm applied to XMIT
    that the CH1837A/8A is either answering a call or
    will comply with the FCC Part 68 requirement for data
    preparing to place a call.
    signals across Tip and Ring.
    2004 Cermetek Microelectronics, Inc.
    Page 2
    Document No. 607-0014 Revision C3 (02/04)
    Cermetek Microelectronics, Inc.
    CH1837A/8A Data Access Arrangement Module
    CH1837A. The user presents all outgoing transmit
    when circuited per Figure 5 herein. Cermetek offers
    signals to the XMIT(-) pin with respect to GND for
    the following end product design guidelines as
    single ended operation or between XMIT(-) and
    suggestions only. These guidelines are intended to
    XMIT(+) for differential operation. This signal must be
    facilitate the usage of Cermetek DAA modules and to
    AC coupled through a 0.1 µ F capacitor present on both
    assist the user with FCC certification of their end
    the XMIT(-) and XMIT(+) pins as shown in Figure 3.
    product.
    For single-ended operation, the outgoing analog signal
    1. Mount the DAA in the final assembly so that it is
    is applied to the XMIT(-) pin with respect to GND. This
    isolated from exposure to any hazardous voltages
    signal must be AC coupled using a 0.1 µ F capacitor as
    within the assembly.
    Adequate separation and
    shown in Figure 3. In single ended signal operation,
    restraint of cables and cords must be provided.
    the XMIT(+) pin must be connected to GND through a
    0.1 µ F capacitor.
    2. Connect to the PSTN line through a standard FCC
    approved RJ-11C jack or equivalent. For RJ-11,
    CH1838A.
    All incoming and outgoing signals are
    use the two center pins .
    presented between T1 and T2. The user must provide
    an external hybrid conversion circuit and/or control the
    3. All PCB traces from the CH1837A/8A TIP and
    flow of the transmit and receive signals into/from the
    RING pins must be at least 0.1 inch spacing from
    CH1838A.
    all other traces or other conducting material. The
    purpose for this spacing is to maintain 1500 VC
    isolation between the incoming PSTN line and the
    RECEIVE SIGNALS
    other traces. PSTN related PCB Traces should
    The incoming analog signal appears across TIP and
    have a width of 0.020 inches or greater.
    RING. The CH1837A/8A does not amplify the receive
    signal. Receive signals can vary from a maximum
    4. TIP and RING PCB traces should be as short as
    strength of -9dBm to below -50dBm.
    possible and should be oriented to prevent direct
    or induced coupling with other signals present on
    CH1837A. The CH1837A derives the incoming signal
    the PCB.
    and presents it at RCV with respect to GND. The user
    must AC couple RCV through a 0.1 µ F capacitor as
    5. The CH1837A/8A processes signals in the millivolt
    indicated in Figure 3.
    range. Even though the CH1837A/8A is designed
    to handle noise in the power supply, steps should
    CH1838A.
    The CH1838A presents the incoming
    be taken to assure that the noise level does not
    signal between T1 and T2. The user must provide an
    exceed 50 mV peak-to-peak. Particular attention
    external hybrid conversion circuit and/or control the
    should be paid to both the power supply and the
    flow of the transmit and receive signals into/from the
    ground line PCB traces.
    CH1838A.
    6. For data calls, FCC Part 68 rules require silence
    on the PSTN line for at least 2 seconds after a
    data call has been completed to allow central
    Attenuation:
    0.0dN
    offices to exchange billing information. Further,
    Input Impedance:
    150K
    Part 68 specifies that the transmit level must not
    Typical Input Signal:
    0dBm or 0.775Vrms with the
    exceed -9dBm.
    Signal referenced to GND and
    AC coupled
    7. For voice calls, the FCC rules require that the end
    product must meet the requirements of Part 68 for
    Out-of-Band Energy, and DTMF Transmit Levels.
    UL RECOGNITION
    To further protect the end product containing the
    CH1837A/8A from field failures caused by large
    HANDLING
    AND
    ASSEMBLY
    transients present on poor quality PSTN lines and to
    RECOMMENDATIONS
    maintain UL recognition, an additional level of external
    The CH1837A/8A DAA Module contains static-
    transient protection is required. Refer to Figure 5 for
    sensitive components and should only be handled by
    mandatory additional protection circuitry.
    personnel and in areas that are properly protected
    against static discharge. Industry standard ESD and
    EOS procedures and precautions should be observed
    DESIGN CONSIDERATIONS
    when handling CH1837A/8A products.
    The CH1837A/8A DAA includes circuitry that couples
    the modem signals to the PSTN line and provides the
    FCC required voltage isolation and surge protection
    2004 Cermetek Microelectronics, Inc.
    Page 3
    Document No. 607-0014 Revision C3 (02/04)
    Cermetek Microelectronics, Inc.
    CH1837A/8A Data Access Arrangement Module
    MOUNTING THE DAA
    There are two mounting techniques recommended for
    physically connecting the CH1837A/8A DAA to a PCB:
    1. Direct soldering.
    2. Sockets.
    Direct Soldering. The CH1837A/8A may be wave
    soldered onto a circuit card. All CH1837A/8A products
    are hermetically sealed and will not be harmed by
    industry standard wave soldering processes.
    To avoid the problems of flux contamination, hand
    soldering is preferred to wave soldering.
    When
    cleaning, use only demonized water.
    Socketing.
    The socketing approach to mounting
    eliminates cleaning and desoldering concerns. When
    the socket is used, it must make a solid connection to
    all pins.
    Failure to do so will cause unreliable or
    intermittent operation.
    When using sockets, steps should be taken to assure
    that the DAA module remains tightly seated in the
    socket after the end product is shipped.
    It is
    recommended that some type of mechanical restraint
    be provided to keep the CH1837A/8A seated to avoid
    any possibility that the CH1837A/8A works loose
    during shipment.
    See Application Note # 130,
    Summary of Recommended Suppliers for a list of
    recommended socket manufacturers.
    FCC (USA) AND DOT (CANADA)
    REGISTRATION
    FCC Part 68 or DOT CS-03 registration of the end
    product containing the CH1837A/8A DAA is normally
    quite simple. The process involves testing the end
    system for compliance and submitting the test data to
    the FCC or DOT for review.
    Typically, independent approved testing labs are
    contracted to perform the required tests on the end
    product and to submit the required paperwork to the
    FCC or DOT. If desired, Cermetek can assist with the
    Registration activity.
    See Application Note # 130,
    Summary of Recommended Suppliers. The user is
    assigned the registration and assumes all risk for
    registration compliance.
    2004 Cermetek Microelectronics, Inc.
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    Document No. 607-0014 Revision C3 (02/04)
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    CH1837A/8A Data Access Arrangement Module
    Table 1. CH1837A Pin Description.
    PIN
    I/O
    CH1837A
    FUNCTION
    1
    I/O
    TIP
    TIP. Direct PSTN line connection.
    2
    I/O
    RING
    RING. Direct PSTN line connection.
    3
    I
    OFFHK
    OFF-HOOK. Used to toggle CH1837A product between On-Hook and Off-Hook.
    When set LOW, CH1837A is On-Hook. When set HIGH, CH1837A is set Off-Hook
    to answer or place a call. See Note 1.
    4
    O
    RI
    RING INDICATION. Indicates the presence of a ring signal between TIP and RING
    pins. RI output is a square wave coincident with the incoming AC ring signal. The
    RI square wave output can be conditioned to produce an envelope of the incoming
    AC ring signal by using the circuit in Figure 4. See Notes 2 and 3.
    5
    O
    RCV
    RECEIVE. Audio output signal with respect to GND. AC couple RCV through
    0.1 µ F capacitor to eliminate any DC offset.
    6
    I
    XMIT(-)
    TRANSMIT(+). Audio input signal. AC couple through 0.1 µ F capacitor. The
    CH1837A can be used in differential mode with XMIT(+) or in single ended mode
    with respect to GND.
    7
    I
    V CC
    POWER SUPPLY. +5V ± 5%. Supply line noise should be less than 50mV peak to
    peak.
    8
    I
    XMIT(+)
    TRANSMIT(-). Audio input signal for CH1837A/Fwhen used in differential mode
    only. Connect to GND through 0.1 µ F capacity when CH1837A used in single
    ended input via PIN 8.
    9
    I
    GND
    GROUND. Supply line noise should be less than 50mV peak to peak.
    Note:
    1. When answering incoming calls in response to a ring indication on RI, internal degradation may occur if OFFHK
    is set HIGH before RI returns to its HIGH state.
    2. For CH1837A, the RI output is 2X the frequency of the incoming ring signal.
    Table 2. CH1838A Pin Description.
    PIN
    I/O
    CH1838A
    FUNCTION
    1
    I/O
    TIP
    TIP. Direct PSTN line connection.
    2
    I/O
    RING
    RING. Direct PSTN line connection.
    3
    I
    OFFHK
    OFF-HOOK. Used to toggle CH1838 product between On-Hook and Off-Hook.
    When set LOW, CH1838 is On-Hook. When set HIGH, CH1838 is set Off-Hook to
    answer or place a call. See Note 1.
    4
    O
    RI
    RING INDICATION. Indicates the presence of a ring signal between TIP and
    RING pins. RI output is a square wave coincident with the incoming AC ring
    signal. The RI square wave output can be conditioned to produce an envelope of
    the incoming AC ring signal by using the circuit in Figure 4. The RI output is 2X
    the frequency of the incoming ring signal.
    5
    I/O
    T1
    RECEIVE. Audio input and output signal with respect to T2.
    6
    N/C
    N/C
    AUDIO INPUT/OUTPUT. Internally not connected. Either let float or connect to
    GND.
    7
    I
    V CC
    POWER SUPPLY. +5V ± 5%. Supply line noise should be less than 50mV peak to
    peak.
    8
    I/O
    T2
    AUDIO INPUT/OUTPUT. Audio input and output signal with respect to T1.
    9
    I
    GND
    GROUND. Supply line noise should be less than 50mV peak to peak.
    Note:
    1. When answering incoming calls in response to a ring indicator on RI, internal degradation may occur if OFFHK
    is set HIGH before RI returns to its HIGH state.
    2004 Cermetek Microelectronics, Inc.
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    Document No. 607-0014 Revision C3 (02/04)
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    CH1837A/8A Data Access Arrangement Module
    Table 3. CH1837A/8A Electrical Specifications.
    Parameter
    Conditions
    Min.
    Typ.
    Max.
    Units
    Logic
    Input HIGH
    2.4
    V
    Input LOW
    0.4
    V
    Input Leakage HIGH
    500
    µ A
    Input Leakage LOW
    -500
    µ A
    Output HIGH
    IOH=0.05mA
    3.0
    V
    Output LOW
    IOL=2.0mA
    0.4
    V
    Isolation Protection
    Between TIP and RING
    CH1837A/8A
    1500
    VAC RMS
    Surge Protection
    Between TIP and RING
    CH1837A/8A
    2212
    V Peak
    Transmission Insertion Loss
    Attenuation between the transmitter input
    PSTN
    line
    at
    1.8kHz
    with
    600ohms
    -0.8
    0
    +0.8
    dB
    termination (flat from 300-4kHz)
    Frequency Response
    (Ref=1800Hz Transit)
    200-4kHz
    -0.3
    +0.3
    dBm
    Distortion Noise-Transmit
    -10dBm transmit power (600Hz)
    -82
    dBm
    Receive Gain
    Gain between PSTN line and receive output -0.5
    0
    +0.5
    dB
    at 1800Hz with 600 ohm resistive termination
    (flat from 300-4kHz)
    Receive Frequency Response
    (Ref = 1800Hz Receive)
    200-4kHz
    -0.3
    +0.3
    dBm
    nd
    rd
    th
    Receive 2 /3 /4
    -10dB at TIP and RING
    -82
    dBm
    Harmonic Distortion
    Noise-Receive
    400Hz-4kHz
    -82
    dBm
    PSTN Line Input Impedance
    At 1800Hz
    550
    600
    650
    Ohm
    On-Hook Impedance
    10
    20
    mOhms
    Loop Current
    48VDC from TIP to RING.
    20
    100
    mA
    Longitudinal Balance
    OH=0 (On-Hook)
    66
    dBm
    OH=1 (Off-Hook)
    66
    dbm
    Return Loss
    1kHz
    25
    dBm
    (Zref=600ohm, 2.16 µ F)
    Trans-Hybrid Loss
    Attenuation between the transmitter input 22
    25
    dB
    and receiver output at 1kHz with 600ohm
    complex termination
    Transmit Input Impedance
    At 1800Hz
    120
    150
    200
    kOhm
    Receive Output Impedance
    At 1800Hz
    10
    100
    Ohms
    Ring Select Sensitivity
    AC voltage between TIP and RING
    38
    V rms
    Hook Switch Control Current
    Drive capable of sourcing current
    4
    mA
    Weight
    20
    gm
    Supply Current
    V CC =+5VDC ± 5%, Off-Hook
    8
    mA
    V CC =+5VDC ± 5%, On-Hook
    5
    mA
    Ringer Equivalence
    Type A
    0.2A
    REN
    2004 Cermetek Microelectronics, Inc.
    Page 6
    Document No. 607-0014 Revision C3 (02/04)
    Cermetek Microelectronics, Inc.
    CH1837A/8A Data Access Arrangement Module
    Figure 5. PSTN Line Interface.
    approval and to maintain UL60950/3 edition
    rd
    1. Currently Limiting PSTN Protection Line
    Device.
    listing.
    Currently limiting devices are mandatory to meet
    B. In most environments, 2 terminal surge
    UL safety standards. For FCC Part 68 approval,
    suppressors are adequate.
    For severe
    the current limiting components identified as F1
    environments, use an external 3 terminal
    and F2 in dashed Box #1 must also survive FCC
    device (as indicated in Figure 5) with an earth
    Part 68 surge testing.
    Refer to Cermetek
    ground.
    Application Note #126, Supplemental PSTN Line
    Protection, for more details. Refer to Application
    Note # 130, Summary of Recommend Suppliers,
    3. EMI/RFI Suppression.
    for a list of suppliers and associated part numbers.
    Additional suppression, if required, may be added
    as described below in Sections 3A-3B without
    adversely affecting FCC Part 68 approval or
    A. A Polyfuse (rated at 0.15 amps) is preferred
    UL60950 listing.
    because it resets automatically upon removal
    of the current flow.
    Non-resettable devices
    are also acceptable. Refer to Application Note
    A. To provide adequate EMI/RFI suppression,
    #130 for a complete list of recommended
    the capacitor/inductor network contained in
    vendors and associated part numbers.
    dashed Box #3 should be located as close to
    the RJ11 Jack as possible.
    Further, this
    network should be provided with an excellent
    B. Resistors (10 carbon film or 1/8 watt
    ground path to the chassis.
    minimum) may be used in Canada, as Canada
    has no requirements that PSTN equipment be
    operational after a Type B surge test.
    B. Capacitors C1 and C2 should not exceed
    0.005 µ f. They must have a rating of 1.5KV
    C. Although CSA CS-03 Part 1 (Canada) follows
    and typically are 0.001 µ f ± 20%. Inductors L1
    the requirements of FCC Part 68 (USA),
    and L2 may be either individual inductors or a
    Cermetek
    recommends
    contacting
    DOT
    dual inductor. Refer to Application Note #130
    (Canada) and/or a certified independent lab to
    for a complete list of recommended vendors
    verify compliance.
    For Canada, use either
    and associated part numbers.
    For UL
    applications, choose capacitors and inductors
    10 resistors (carbon film or SMD parts 1/8
    that are UL60950 listed. The actual values of
    watt minimum) as described in paragraph B
    the components used may vary depending on
    above.
    the end product design.
    2. Over Voltage and Lightning Protection.
    A. The required UL60950 and FCC Part 68 surge
    protection (identified as D1 in dashed Box 2)
    must be supplied externally. The purchaser
    must include some form of surge protection as
    described herein to obtain FCC Part 68
    2004 Cermetek Microelectronics, Inc.
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    Document No. 607-0014 Revision C3 (02/04)
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    CH1837A/8A Data Access Arrangement Module
    Table 4. Summary CH1837A/8A Product Features.
    Model
    Summary of Features
    Operating Temperature
    CH1837A
    33.6kbps DAA, 2-to-4 Wire Conversion, FCC Part 68 Compliant,
    0 ° C to +70 ° C
    UL60950/3 edition Listed. RI is 2X the incoming ring frequency.
    rd
    rd
    CH1838A
    33.6kbps DAA, FCC Part 68 Compliant, UL60950/3
    edition Listed
    0 ° C to +70 ° C
    Special Order Option to Standard CH1837A product.
    Notes:
    1. Pins are 0.010 inches X 0.020 inches.
    *2. Nominal pin length is 0.200 inches for CH1837A/8A.
    3. Nominal case tolerance ± 0.02 inches.
    4. Nominal pin tolerance ± 0.03 inches.
    Figure 6.
    Physical Dimensions.
    Cermetek reserves the right to make changes in specifications at any time and without notice. The information furnished by
    Cermetek in this publication is believed to be accurate and reliable. However, Cermetek assumes no responsibility for its use, or for
    any infringements of patents or other rights of third parties resulting from its use. No license is granted under any patents or patent
    rights of Cermetek.
    Cermetek provides the user with a FCC/DOT Approved or Approvable device. However, Cermetek does not have influence nor
    over knowledge of the specific user application environment. Therefore, for FCC Approved or Approvable devices, the user
    assumes all risk for maintaining compliance to registration.
    Printed in U.S.A
    406 TASMAN DRIVE | SUNNYVALE CA 94089 | LOCAL: 408-752-5000 | TOLL FREE: 1-800-882-6271 | FAX: 408-752-5004
    CERMETEK WEB SITE: http://www.cermetek.com | EMAIL: sales@cermetek.com
    iModem Network WEB SITE: http://www.imodem.net/ or https://sunnyvale.imodem.net/
    2004 Cermetek Microelectronics, Inc.
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    Document No. 607-0014 Revision C3 (02/04)