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Catalog # 303121 - Model 4121 Auto Fallback & Recover DB25 A/B Switch

    Auto Fallback & Recover DB25 A/B SwitchAuto Fallback & Recover DB25 A/B SwitchAuto Fallback & Recover DB25 A/B Switch
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    • Auto Fallback & Recover DB25 A/B Switch
    • Auto Fallback & Recover DB25 A/B Switch
    • Auto Fallback & Recover DB25 A/B Switch
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Catalog No: 303121
Model No: 4121
Switch Media:Copper
Channels per Switch Chassis:1
Electronic Switches/Power Required:PathWay® Copper
Remote Control:Auto Fallback, RS232 Serial
Enclosure Configuration:Desktop
Auto Fallback:Data Monitor Port A
Pins Switched:1-8, 20
Remote Port:DB9
Local Control:Pushbutton


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Products shall be shipped F.O.B. Electro Standards' facility. Title to and risk of loss or damage to the products shall pass to you upon Electro Standards delivery of the products to a carrier for shipment. Title to software will remain with the applicable licensor. Electro Standards' prices do not include shipping and handling charges. Electro Standards reserves the right to use its own discretion in the manner and routing of shipments. Electro Standards shall be permitted to deliver products in separate lots.

Shipping Return Policy

  • To return an item, contact Electro Standards at 401-943-1164 to obtain a Return Material Authorization (RMA) number. RMA numbers are valid for 30 days after the date of the shipment and cannot be extended or re-issued. We are unable to accept returns without an RMA number.
  • All returns except those of defective product are subject to a 15% restocking fee, and additional charges for handling or freight are refunded only in cases of defective products.
  • Return freight must be shipped prepaid. We recommend that you insure the package as you are responsible for risk of loss on all returned packages. We recommend that all cartons are properly packed as Electro Standards is not responsible for product damaged en route. We do not issue call tags for product returns.
  • Returned product must be clean, undamaged, and complete with all manuals, accessories, documents and packaging. The items must be in a resalable condition.
  • The product must have with it a copy of the original invoice or packing slip and the appropriate RMA paperwork.
  • If your item is not working properly, please contact Electro Standards at 401-943-1164 for help in trouble-shooting your application.
  • If the product is defective, Electro Standards will repair or replace that item (at our discretion) upon receipt and evaluation of the original product.
  • Electro Standards reserves the right to authorize product returns after 30 days from the invoice date in some cases. If the product is accepted after 30 days, credit will be issued toward future pruchases only and some additional restocking charges may be applied.
  • All credits from RMAs must be used within one calendar year of issue.

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Model 4121 Automatic Fallback and Recovery DB25 A/B Switch with RS232 Remote Control

  • This Smart Switch provides a "Fallback" data path "B" based on loss of Data Activity on Port "A", and a "Recovery" to "A" when Data Activity returns!

  • Data Activity "Watch Dog" Switch keep data flowing!


  • PORT CONNECTORS: (3) DB25 female connectors labeled A, B, and COMMON. 
  • FRONT PANEL CONTROL: (1) Manual pushbutton allows local switching.
  • DISPLAY: (2) Front panel LEDs display switch position and power status.
  • REMOTE CONTROL: (1) DB9 female connector on rear panel accepts ASCII RS232 Serial Data for Remote Control operation.
  • POWER: UL approved 100VAC/240VAC 50 Hz/60Hz wall mount power module supplies 12VDC, 500 mA to the unit.
  • DIMENSIONS: Desktop configuration 8.15" W x 2.41" H x 7.30" D (20.8 x 6.2 x 18.6 cm) 
  • WEIGHT:  Approximately 1.9 lbs. (0.9 kg) 
  • DB25 AUTO FALLBACK & RECOVERY APPLICATION: Ideal for automatic fallback applications based on loss of data on Port A. Monitor data activity. Smart switch provides a "Fallback" data path "B" based on loss of Data Activity on Port "A". The diagram illlustrates an Off-Site Remote management via the DB9 Remote port (ASCII RS232 Serial Data Remote).

PathWay® Model 4121 Automatic Fallback and Recovery Application drawing.

Ideal for automatic fallback applications based on loss of data on Port A. Monitor data activity. Smart switch provides a "Fallback" data path "B" based on loss of Data Activity on Port "A". The diagram illustrates a DB9 Remote port that accepts RS232 Serial data commands.

PathWay® Model 4121 DB25 A/B Auto Fallback Application


  • Allows access to two networks from one COMMON network or device.
  • The switch ports are transparent to data.
  • Pins 1-8, 11, 14-21 and 24 of the DB25 interface are switched via break-before-make electromechanical relays.
  • The unit maintains last set position on power loss and continues to pass data.
  • Front panel pushbutton control.
  • Remote RS232 ASCII commands that allow the user to; control switch position, lockout front panel operations, change the Fallback Mode, set the delay time, select the pins monitored, change the Recovery Mode, obtain switch status, as well as, query firmware version number, query serial number, and enable/disable autosend of switch positions.
  • Remote port Contact Closure status on pins 6, 7, and 8 provide dry contact logic to obtain the present switch position.
  • Automatic Fallback and Recovery Mode operates based on data monitoring on signal pins 2 and 3 of port A.
  • Recovery Mode can be set to either automatic or manual.
  • Front panel LED's display present position, mode and power status.
  • Attractive all metal black box packaging provides EMI/RFI shielding.
  • Custom length DB25 cables available for your switch installation. 

The PathWay® Model 4121 Automatic Fallback and Recovery DB25 A/B Switch with RS232 Remote Control allows the user the capability of sharing a single port interface device connected to the "COMMON" port among two other devices connected to the "A" and "B: ports with remote access functionality.  The Model 4121 is packaged in a slim desktop style enclosure.

The switch may be controlled locally by manually operating the front panel pushbutton, or remotely through the DB9 Female Serial Interface Remote port located on the rear of the unit. The front panel LED display indicates the switch position, switch mode, and power status.

The unit monitors data activity on port "A". If the unit is in the A position and activity is lost for the duration of the set delay time, the unit automatically switches to the B position.  Depending on the Recovery Mode set, the unit will then either remain in the B position until commanded to switch to the A position by the pushbutton or Remote or switch back to the A position automatically when the signal returns.

Wide Range Power Option Available: (Cat No 517277)  CE, RoHS, and UL listed table mount power module, 100VAC/240VAC, 50/60Hz for use in place of the standard power module that is included with the unit.  Has IEC 60320 C14 inlet. Ideal for international applications.

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All data switch boxes, data communication products, and data acquisition products are subject to a one year warranty against manufacturing defects.  The limit of ESL liability is limited to the cost of the ESL product provided.

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