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Asynchronous Local RS-232 Multiplexor - 8-Port

A mux that won’t shortchange you for short distances.


Please call 877-877-2269 for a replacement product or part.
Extended Double Diamond™ Warranty Available (3 Additional Year)

Product Features

  • Time-division multiplexors with integral short-haul modems.
  • Economical alternative to stat muxes.
  • Up to 16 async ports.


  • Screw terminal interface on composite port.
  • Support speeds up to 64 kbps per port.
  • Operate at distances up to 3000 feet (914.4 m) over two 24 AWG twisted-pair cables.
  • Plug-and-play installation—no option switches to set.

  • If you're looking for an economical alternative to leased-line modems and statistical multiplexors, BLACK BOX® Asynchronous Local RS-232 Multiplexors give you speed and savings in your async environment!

    Here's an economical alternative to more expensive stat muxes.

    Our Async Local RS-232 Muxes are time-division multiplexors that support 4-channel speeds up to 64 kbps, 8-channel speeds up to 38.4 kbps, and 16-channel speeds up to 19.2 kbps. All ports operate at maximum throughput levels with virtually no multiplexing delay. All models have an internal line driver for twisted pair. The units' internal line drivers provide limited-distance communication over private networks with point-to-point twisted-pair cabling.

    Our Asynchronous Local RS-232 Multiplexors automatically adapt port speeds to the rates of your individual terminals—no clock source is required. Plus, synchronization between multiplexors is maintained automatically.

    Tech Specs

    Connectors Channel: 38887: (4) RJ-45; 38889: (8) RJ-45; 38891: (16) RJ-45; Composite: 4-screw terminal block
    Distance (Maximum) 3000 ft. (914.4 m) on (2) twisted-pair cable (24 AWG)
    Interface Channel: RS-232; Composite: 4-wire terminal block
    Multiplexing Technique Time division
    Operation Full-duplex
    Power 115-VAC, 60-Hz external power supply
    Protocol Async
    Size 38887, 38889: 1.7"H x 7"W x 5.3"D (4.3 x 17.8 x 13.5 cm); 38891: 2.2"H x 7"W x 5.3"D (5.6 x 17.8 x 13.5 cm)
    Speed (Maximum) 38887: 64 kbps per port; 38889: 38.4 kbps per port; 38891: 19.2 kbps per port

    NOTE: Must be used in pairs.

    These products work with:
    • CAT5 100-MHz Solid-Conductor Cable, 4-Pair, Straight-Pinned (EYN737MS)
    Questions? Contact our FREE Tech Support.

    * 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: $47.00

    Extended 3 Year Warranty Available

    Protect your purchase with an additional 3 Year Double Diamond™ warranty!
    Cost: $93.99


    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 Asynchronous Local RS-232 Multiplexor - 8-Port comes with a standard 1 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.