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Modbus ASCII/RTU Serial Server, RS-485


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


  • Handles most Modbus network configurations.
  • Supports links to 10- and 100-Mbps networks, detecting speeds automatically.
  • Serial data rates up to 115.2 kbps.
  • RS-485 model supports connections up to 32 serial Modbus devices.
  • Compact with clips for mounting on a DIN rail or on a panel.
  • Operate in harsh environments.

  • This DIN rail-mountable serial server converts industrial ASCII and RTU protocols to TCP protocol for communications between a Modbus and a 10- or 100-Mbps Ethernet network.

    Migrating to an Ethernet-based system in your industrial application? Well don‘t replace the older Modbus equipment you‘ve already invested in. Just use one of these easy-to-integrate boxes to translate the signals between older and newer protocols.

    Intelligent protocol translation.
    The Black Box® Modbus RS-485 ASCII/RTU Serial Server gives you a convenient and highly affordable way to link your Ethernet TCP/IP networks to any Modbus ASCII or RTU serial device in your factory or industrial application.

    The serial server translates between Modbus ASCII/RTU protocols and Modbus TCP protocols, formatting communications so the binary coding and CRC error checking in the RTU transmission and the characters in the ASCII format can be effectively carried across a TCP/IP network. PLCs can then talk to sensors, meters, scales, and other industrial monitoring and automation instruments.

    Flexible Modbus integration.
    Two versions of the Modbus ASCII/RTU Serial Servers are available. The LES41A connects to a Modbus device with an RS-232 interface, and supports TD, RD, and GND RS-232 lines. The LES42A works with a Modbus device with a four-wire RS-422 interface, or a two- or four-wire RS-485 interface, and supports TDA(-), TDB(+), RDA(-), and RDB(+) RS-422/485 lines.

    What‘s more, they work in most Modbus setups. Over a TCP/IP network, they enable:
  • Modbus ASCII/RTU slave devices to communicate with Modbus TCP/IP master units.
  • Modbus ASCII/RTU master devices to communicate with Modbus ASCII/RTU master devices.

    Easy network installation.
    These serial servers are also super easy to install. You typically connect the serial server to your 10-/100-Mbps network via a hub switch or router using standard straight-through CAT5 cable. But you can also connect it directly to your Ethernet network with a crossover cable. The Modbus RS-232 or RS-485 ASCII/RTU Serial Servers autodetect and adapt to speed of connected devices or your network.

    The included device installer software enables you to use a Telnet connection to discover the Modbus RS-232 or RS-485 ASCII/RTU Serial Server on the network and assign it an IP address. You use the same utility to easily configure master/slave, serial interface, and advanced Modbus settings, as well as monitor the serial server and verify its status. For at-a-glance monitoring, LEDs on the units indicate link integrity and data transfer activity.

    NOTE: RS-232 version also available.

  • Tech Specs

    CE Approval Yes
    Connectors Network: (1) RJ-45; Serial: LES41A: (1) DB9 M (RS-232); LES42A: (1) 5-screw terminal block (RS-485); Power: (1) 2-screw terminal block
    Indicators LEDs: Link Integrity, Activity, Power
    IP Address Assignment Static IP or DHCP
    Operating Environment Temperature: -4 to +176° F (-40 to 85° C); Humidity: 10 to 90%, noncondensing
    Operating Systems Supported Windows® 98/2000/ME, Windows XP, Windows NT® 4.0
    Parity None, Even, Odd
    Power Input: 10-30 VDC (power supply not included [PSD100])
    Protocols Supported TCP, UDP, DHCP, SNMP, Telnet, ICMP, ARP, TFTP, Modbus ASCII, Modbus RTU, Modbus/TCP
    Serial Data Bits 7 or 8
    Serial Data Rates 300, 600, 1200, 2400, 3600, 4800, 9600 bps; 19.2, 38.4, 57.6, 115 kbps
    Serial Protection LES41A: 12 V TVS; LES42A: 5 V TVS
    Serial Stop Bits 1, 2
    Size 1.25"H x 4.5"W x 4.75"D (3.2 x 11.4 x 12.1 cm)

    * 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: $33.80

    Extended 3 Year Warranty Available

    Protect your purchase with an additional 3 Year Double Diamond™ warranty!
    Cost: $67.59


    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 Modbus ASCII/RTU Serial Server, RS-485 comes with a standard 5 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.