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  It's better to forfeit moments of your life

than to forfeit your life in a moment.  

Intentional or unintentional speeding can result in costly outcome.    SpeedWatcher   is the answer.  

SAS - Speed Activated Switch



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Vehicle Speeding Alarm

The Speed Activated Switch is designed for applications which call for a switch that can respond to the vehicle speed. The SAS can be installed along with other after market automotive instruments such as Turbochargers and Active Spoilers.
The Speed Activated Switch is capable of sinking up to 0.75Amp to energize a relay where yet a higher current is needed to run electric motors and other devices. The SAS has an LED which indicates the state of the internal switch.
The Speed Activated Switch is rugged, durable, reliable, and accurate. It can be installed in minutes in any domestic or foreign make and model car.
The Speed Activated Switch measures 3" X 2" X 1" and can be conveniently mounted under the dashboard. With an adjustable threshold, the SAS can be set to any speed - even as low as 10 MPH.

Speed Activated Switch 12V

Speed Activated Switch 24V

Our legacy Speed Activated Switch has been
sold around the world for the past five years.

The 24 volt model of the SAS has been
designed for use on trucks and buses.



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VSA Rx318-08 vs. VSA Rx318-28

The differences between the Rx318-08 and Rx318-28 models of the Speed Activated Switch are in the typical operating voltage, the operating voltage range and the absolute maximum voltage rating of the devices.

How Does it Work?

  • This device allows you to set a chosen speed limit.
  • You set this limit by a simple to use, single-turn knob.
  • The Speed Activated Switch provides an output capabele of energizing an external relay, used to activate external flashing lights, Horns, electric motores etc.
  • The internal switch remains ON for as long as you are exceeding the set limit.
  • Once you reduce your speed below the set limit, the internal switch will turn OFF .
  • For better understanding of how it works please download and run the VSA Simulator.

Features and Functions:

  • Small and attractive.
  • Simple to use - one single turn knob.
  • Turns on simultaneously with car ignition.
  • The internal switch is capable of continues sinking 0.75Amp
  • Quick installation - takes less than 15 minutes to a mechanic.
  • Easy to follow installation instructions - for Do-It-Yourself customers.
  • No batteries required.

Product Highlights

  • You can change your "speed threshold" setting as often as you like by turning the knob!
  • The Speed Activated Switch is inexpensive way to automaticaly activate /diactivate devices based on vehicle's speed.
  • The VSA318-08 is the most cost effective Speed Activated Switch. on the market.

Customer Product Reviews

Product Specifications

Operating Voltage:





Operating Voltage Range:


    +9.8VDC to +15VDC


    +18VDC to +30VDC

Absolute Maximum Rating:





Over Voltage:


Reverse Voltage:


Power Consumption:


Int. Switch Max Current:


Size: (W, H, L) (In/cm)

3", 2", 1" / 7.6cm 5.1cm 2.5cm


2 oz. / 56gr.


Molded ABS

Operating Temp.:

-38C to +68C / -36F to +155F

Storage Temp.:

-48C to +85C / -55F to +185F


5% to 95% R.H. non-condensing

Adjustable Speed Limit:

10 - 160 MPH / 15 - 250 KPH

Sensitivity / Resolution:

0.05 MPH / 0.1 KPH


< +/- 0.5%

VSS Input Type:


VSS Input Threshold:


VSS Input Volt. Low:

< 3V

VSS Input Volt. High:

> 6V

VSS Input Noise Rejection:

BI Noise Reduction Circuitry

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