Black Box ME444A-530-R3, ME444AE-R3, ME445C-X.21, ME445C-35, ME444A-R3, ME445C-530 Modulation Timing

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256-KBPS LINE DRIVER (V.35, RS-530, OR X.21)

NOTE

In multipoint applications, do not use the 0-msec option for the RTS–CTS delay.

2.2.2MODULATION TIMING

This circuit supplies the transmit clock to the encoder. Three clock sources are available on the XMT CLK jumper (J3):

INT—Internal clock. From the modem’s internal crystal oscillator.

EXT—External clock. From DTE.

RCV—Receive clock. Recovered from the receive signal.

There is also an ASY (asynchronous) setting, but this has no function and should not be selected.

2.2.3SIGNAL LEVELS

Two options are available for the transmit and receive signal levels: 0 and -6 dBm. You can control the transmit level with the XMT LVL jumper. You can control the receive level with the RCV LVL jumper.

2.2.4RECEIVER

The receiver comprises several circuits, as shown in the block diagram (see Figure 2-1):

The RECEIVE FILTER, which removes all the out-band frequencies.

The EQUALIZER, which comprises several equalizers activated according to data rate.

The digital Automatic Gain Control (AGC), which automatically compensates for the attenuation of the line.

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Contents Kbps Line Driver FCC and IC RFI Statements Safety Warnings Declaration of Conformity Kbps Line Driver V.35, RS-530, or NOM Statement Trademarks Used in this Manual Contents Flow Control None SpecificationsSpecifications Physical Description IntroductionFunctional Description Line driver block diagramModulation Timing Point-to-point application ApplicationsTail-circuit application Placement of the Standalone Version ConfigurationInstalling the Card Version in the RackNest 2/14 Description of the Racknest 2/14’S Power Supply User-configurable options Configuring the Standalone or Card VersionUser-configurable options Layout of the 256-kbps Line Driver circuit board Kbps Line Driver V.35, RS-530, or Installing the Standalone Version in 19-Inch Racks InstallationInstalling a single unit in a 19-inch rack Installing two units in a 19-inch rack Installing a card in the RackNest 2/14 Installing the 256-kbps Line Driver Rackmount Card VersionRackNest 2/14 illustrated Function Installation Kbps Line Driver V.35, RS-530, or Signal ITU-TSS Lead Name Abbrev Circuit Type Rack Norm Nest PIN Pinout of the V.35 standalone’s M/34 connector DB25 DA15 Connecting Data Cables Line Connection Installation Operation Controls and IndicatorsOperation Indicators Operating ProcedureBit-Error-Rate Tester Bert TroubleshootingLoop Tests Bert using loops Local Analog Loopback Modem Self-TestLocal analog loopback Remote Digital Loopback Remote digital loopback Local Digital LoopbackLocal digital loopback Calling Black BoxShipping and Packaging 19-AWG 22-AWG 24-AWG 26-AWG Kbps Miles Appendix Maximum DistancesCopyright 2004. Black Box Corporation. All rights reserved