RAD MSD 8-Channel Modem Sharing Device 

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RAD MSD 8-Channel Modem Sharing Device


  • The modem sharing device, MSD, enables up to 8 terminals to share a master modem or multiplexer in a multipoint environment. It has four channels which can be expanded via channel doublers to optimize the use of computer lines.
  • The main channel broadcasts information to subchannels in parallel. Subchannels contend to transmit to the main channel by data contention or by activating RTS. LEDs indicate which subchannel is selected, as well as the main channel activity.
  • If RTS or data is raised, the subchannel's transmit data and control signals are connected to the main channel. When RTS drops, or 16 idle bits are transmitted, control circuitry is switched to monitor the other sub-channels, enabling them to contend for the main channel. The Data Contention feature allows connection of a tail circuit modem to an MSD subchannel.

Note: This application requires a buffer (not incorporated in the unit) to accommodate the difference in phase.

  • Nine LEDs, MAIN and 1 to 8, indicate data activity on the corresponding channels.
  • MSD operates with synchronous or asynchronous equipment and generates timing signals using external clocks from the main channel.
  • Up to 8 channels
  • Synchronous and asynchronous
  • Data rates up to 19.2 kbps
  • Cascadable
  • RTS or data contention
  • Operates without AC supply
  • Easy to install and configure

4-channel Modem Sharing Device

Channel Doubler for connection of up to four additional channels 





RAD Products

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email us at sales@data-connect.com
or call 301-924-7400