TELEBYTE TECHNOLOGY, INC.

MODEL 420

Modem Type               Data (synchronous)
Maximum Data Rate        128Kbps
Data Bus                 External
Data Modulation Protocol Proprietary

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                                CONNECTIONS

         Purpose            Location           Purpose           Location

  DC power                     CN1       Receive                   CN4

  RS-232/422                   CN2       Transmit                  CN5

  Ground                       CN3

          CARRIER ON

  Setting          SW2/C

  » Always on        On

  RTS high          Off

                                  GROUND

  Setting                                              JP1

  » Frame and signal ground connected           Pins 1 & 2 closed

  Frame and signal ground separate              Pins 3 & 4 closed

                IMPEDANCE

  Setting                    JP2

  » 135 Ohms(low)     Pins 1 & 4 closed

  High                Pins 3 & 4 closed

                                LINE SPEED

  Speed       SW1/A     SW1/B      SW1/C     SW1/D      SW1/E     SW1/F

  32Kbps        Up       Down      Down       Down      Down       Down

  48Kbps       Down       Up       Down       Down      Down       Down

  56Kbps       Down      Down       Up        Down      Down       Down

  » 64Kbps     Down      Down      Down        Up       Down       Down

  72Kbps       Down      Down      Down       Down       Up        Down

  128Kbps      Down      Down      Down       Down      Down        Up

       RECEIVE CLOCK

  Setting         SW/H

  » Disabled      Down

  Enabled          Up

              RTS/CTS DELAY

  Setting         SW2/A        SW2/B

  » Disabled       Off          Off

  7ms              On           Off

  60ms             Off           On

   TRANSMIT CLOCK SOURCE

  Setting         SW1/G

  » Internal      Down

  External         Up

  FACTORY CONFIGURED SETTINGS

     Jumper         Setting

     SW2/D          Not used

                          DIAGNOSTIC LED(S)

    LED        Color       Status               Condition

    PWR         Red          On                Power is on

    PWR         Red         Off                Power is off

     TD         Red          On         Modem is transmitting data

     TD         Red         Off       Modem is not transmitting data

     RD         Red          On          Modem is receiving data

     RD         Red         Off        Modem is not receiving data

    RTS         Red          On             RTS signal is high

    RTS         Red         Off             RTS signal is low

    DCD         Red          On          Carrier signal detected

    DCD         Red         Off        Carrier signal not detected

     TM         Red          On           Modem is in test mode

     TM         Red         Off           Modem is in test mode