401-943-1164 / US & Canada Toll Free: 877-943-1164

Model 4124 DB9 A/B Switch, Automatic Fallback Catalog # 304124

    DB9 A/B Switch, Automatic FallbackDB9 A/B Switch, Automatic FallbackDB9 A/B Switch, Automatic FallbackDB9 A/B Switch, Automatic Fallback
Click image to enlarge
    • DB9 A/B Switch, Automatic Fallback
    • DB9 A/B Switch, Automatic Fallback
    • DB9 A/B Switch, Automatic Fallback
    • DB9 A/B Switch, Automatic Fallback
Base Price:
Catalog No: 304124
Model No: 4124
Product Type:Switches: Copper
Cable Type/Port Connector:DB9 Switch Ports
Channels per Switch Chassis:1
Electronic Switches/Power Required:PathWay® Copper
Remote Control:Auto Fallback, Contact Closure
Auto Fallback:Data Monitor Port A, Pins 2 & 3
Pins Switched:9
Remote Port:DB9
Local Control:Pushbutton
Feature:Mounting Bolts on Bottom Panel, Ideal for Onboard Ship Use


Shipping Terms

Shipments are made via UPS Ground, unless otherwise specified. Freight charges are prepaid and added to your invoice. We can estimate the freight costs for you.

We can ship freight collect on your account, just provide your UPS Account Number.

We can also ship via the carrier of your choice. Provide the details and your account number.

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.

Ask a Question

Protected Document Request


Path Way® Remotely Controllable Network Switch, DB9, Auto Fallback
Model 4124 DB9 A/B Automatic Fallback Switch with Contact Closure Remote Port

  • Automatic fallback based on loss of data on port "A"

  • Special mounting hardware for on-board ship use.


  • PORT CONNECTORS: (2) DB9(F) connectors labeled A, and B, (1) DB9(M) connector labeled COMMON.
  • FRONT PANEL CONTROL: (1) Pushbutton for local switch control.
  • DISPLAY: (2) Front panel LED’s display switch position and power status.
  • REMOTE: (1) DB9(F) connector on rear panel accepts contact closure switch commands for Remote Control operation.
  • POWER: UL approved 100VAC-240VAC, 50Hz-60Hz wall mount power module supplies 12 VDC, 500mA to the unit.
  • Has 2-prong, US, non-polarized plug.
  • DIMENSIONS: Desktop, 7.9” W x 2” H x 7.25” D. (20.0 x 5.08 x 18.4 cm)
  • WEIGHT: Approximately 2.8 lbs. (1.27 kg)

PathWay® Model 4124 DB9 A/B Auto Fallback Application with Contact Closure Remote:

The diagram illustrates a single device connected to the DB9 COMMON port sharing between two other devices connected to the DB9 ports labeled PRIMARY line and SECONDARY line. The Automatic fallback is based on loss of data on Port A.  A user can lockout front panel operations and obtain switch status via the DB9 REMOTE port via contact closure commands. Great for on-board ship use! (Special mounting steel pass-through nuts mounted internally to bottom of enclosure for desktop mounting.)

PathWay Model 7124 DB9 A/B Fallback Switch Application


  • Ideal for fallback applications.
  • The switch ports are transparent to all data.
  • All pins of the DB9 interface are switched via break-before-make electromechanical relays.
  • Automatic Fallback Mode operates based on data monitoring of the differential RS422 signal on pins 2 and 3 of the "A" port and automatic switching occurs after 3 seconds of data loss.
  • All switched signals are passed via latching copper contact relays that maintain their position and continuity in the event of a power loss.
  • Control of the switch position from a Contact Closure Remote Port.
  • Contact Closure allows the user to control switch position, lockout front panel operations and obtain switch status.
  • Front panel LEDs display switch position, the switch mode (automatic fallback or manual) as well as power status.
  • Rugged anodized aluminum black box packaging provides EMI/RFI shielding.
  • Special mounting steel pass-through nuts mounted internally to bottom of enclosure for desktop mounting of on-board ship use.

The PathWay® Model 4124 DB9 A/B Automatic Fallback Switch with Contact Control Remote Port, 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.  Remote Control access can be accomplished through the Contact Closure Remote Port.

When in automatic fallback mode the unit monitors data activity on port A.  If activity is lost, the unit switches to position B.  The Model 4124 will maintain its connection to port B until data activity is detected on port A, at which time the unit will automatically return to the A position.  If no data is present on either port A or on port B, the unit will stay in the B position and continue to monitor for data.  The user can override automatic fallback operation from the front panel or Remote Port and force the unit to operate as an A/B switch.

  • Data Activity "Watch Dog" Switch
  • Keeps Data Flowing!
  • Don't forget to order DB9 Cables!


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

This high-quality network switch is available to city, state, and federal government purchasers at a discounted price and favorable payment and shipping terms via GSA Schedule GS-35F-0286V. Click here for GSA details.

Model 4124 is available to government purchasers on our GSA Schedule GS-35F-0286V. Call for discounted price and terms.

Electro Standards can supply all your Network Cable requirements. Click here to reach our CABLES, COPPER NETWORK Webpage.

For custom network switches call our friendly customer support staff at 401-943-1164, email eslab@electrostandards.com, or complete our online form: /Products-Custom/Copper-Switch/

All data switches, 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.

*Prices online are subject to change and verification.

All ESL products are available for export.

Electro Standards welcomes International inquiries: commutateur d'ordinateur,  equipo interruptor, interruttore del calcolatore, interruptor do computador, dator switch. 

Available Combo Deals