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4 Port RS232 Line Sharing Device

Expand leased line, polled environments without adding computer ports or communications links.


Limited Quantity In Stock
Typically Ships within One Week
Extended Double Diamond™ Warranty Available (3 Additional Year)

*Required field

Product Features

  • Enables multiple sync/async terminal or DTE devices operating in a polled environment to share one modem.


  • Increases network efficiency.
  • Transparent to data.
  • Fully cascadable.
  • Individual subchannel enable/disable switches.
  • ±15 kV ESD protection.

  • The Modem Sharing Device (MSD) provides the network manager with a cost-effective way of expanding existing, leased-line, polled networks without adding computer ports or communications links. Up to four terminals can share the same port and communications link using the contention and control protocols normally resident in the host hardware and software. Once installed, system and network efficiency are increased through higher host processor utilization coupled with the significant decrease in idle time between host/terminal traffic sessions.

    Ideal for either synchronous or asynchronous network environments, the MSDs are protocol transparent at data rates up to 128 Kbps. Data arriving at the master port is continually broadcast to all subchannels. The attached terminal device that raises the RTS control signal is automatically given control of the MSD until data transmission is complete. Clocking is accomplished from the attached modem.

    The MSDs incorporate optional anti-streaming circuitry. If enabled, anti-streaming will automatically remove a defective terminal from service if the data/control criteria is present for the user-predefined selection period.

    Housed in a sturdy metal enclosure and equipped with an internal 110/220-VAC switch-selectable linear power supply, the MSDs will provide in excess of 100,000 hours of reliable service.

    Tech Specs

    Altitude 0 to 10,000 feet
    Anti-Streaming Automatic: Selectable time out intervals; Disable: Selectable via dip switch
    Approvals UL 60950-1:2003, CAN/CSA-C22.2 No. 60950-1:2003, CE Safety EN60950 and CE EMC EN300-386-2
    Data Format Data transparent at all data rates
    Data Rate Up to 128 Kbps
    Dimensions 1.75”H x 13.35”W x 9”D (4.4 x 33.1 x 22.9 cm)
    Environmental Relative Humidity: 5 to 95% non-condensing
    Indicators Power, Transmit Data, Receive Data, Channel Active, Channel Stream
    Interface EIA RS-232, CCITT V.24 using DB-25 female connectors, ±15KV ESD protection
    Operating Temperature 32° to 122° F (0° to 50° C)
    Power 100–120 to 200–220VAC @ 10%, 50/60Hz, 0.16/0.08A, External 110/220 volt select switch, IEC Power Inlet, (2) 5-mm fuses
    Terminal Service Modes Scanning or Priority
    Timing External; from attached modem
    Weight 4.5 lb. (2.1 kg)

    * Technical specification weight is the unit weight. It is not the packaged shipping weight. For shipping weight, please contact Black Box customer service at 877-877-2269.



    Double Diamond Warranty

    Extended 1 Year Warranty Available

    Protect your purchase with an additional 1 Year Double Diamond™ warranty!
    Cost: $59.60

    Extended 3 Year Warranty Available

    Protect your purchase with an additional 3 Year Double Diamond™ warranty!
    Cost: $119.19


    Double Diamond™ Warranty (Standard)

    Take the risk out of equipment purchases with the Double Diamond™ Warranty from Black Box Network Services.

    The Double Diamond Warranty is our warranty that protects your Black Box® brand products* from accidental damage, including drops, water, and power surges.

    The 4 Port RS232 Line Sharing Device comes with a standard 3 Year Double Diamond™ Warranty (Standard) already included.

    During the warranty period, Black Box Network Services will repair or replace your damaged equipment within one week of receipt at NO CHARGE!*

    Plus, get an Extended Double Diamond Warranty.

    You can also extend your warranty or protect a previously purchased Black Box® brand product** for an additional year—for only 10% of the purchase price! Or, extend your coverage for a full three years for only 20% of the purchase price!

    Ordering an extended warranty is easy: When viewing a product in your shopping cart, just select the one or three years of additional coverage in the dropdown menu under “Warranty Options.” For details, contact Customer Service at 724-746-5500.

    * Warranty subject to certain exclusions and limitations ** Certain products may not be eligible.

    What’s more, we also have a 45-day return policy. Simply call Customer Service for a Return Authorization (RA) number, return your product in new condition and in the original package, and receive a full refund.