Pi-Lit® Technology Questions and Information


Random flashing lamps provide no guidance and unnecessary warning.  Random flashing lamps are great behind the pizza shop to warn pedestrians of the sewer hole being dug in the parking lot.  When a driver approaches a work zone or incident on the road way, they are well aware of an event ahead.  What they need is guidance.  Sequential-flashing lamps scream out “Follow Me!” to approaching drivers.  Numerous academic and DOT studies reveal that drivers slow sooner and move over more effectively when presented with a sequential-flashing string of lamps.  An arrow board is great.  They are expensive.  From a distance a string of sequential-flashing lamps projects a 100-foot or if you prefer, a 1,000-foot flashing arrow directing traffic around the area of concern.

The European Union has been using sequential lamps for two decades.  Sequential lamps are mandated at work zone entries in the U.K., as well as Italy and many other countries. Now, in the U.S., states such as Pennsylvania, Massachusetts, North Carolina, Missouri, and others have done their homework and see the safety benefits of sequential work zone lamps and sequential LED electronic flares (to replace incendiary flares).

Sequential-flashing warning lamps are described in the Federal and in every state DOT MUTCD (Manual of Uniform Traffic Control Devices- section 6F.83). The lamp is considered a warning lamp and must meet I.T.E. (Institute of Transportation Engineers) specifications for Type A warning lamp.

Technology! It simply wasn’t up to the task prior to 2005 or so.  Prior to 2005 the few deployments in the E.U. required “hard-wire” connections with power and sequencing signals being sent from lamp to lamp by a wire.  So, behind the mounting device (barrel, cone, etc.) you would see a coil of wire running to each lamp.  Recently, electronic circuity and radio-frequency or infra-red technology has provided the tools necessary to sequence lamps without wires and to do so efficiently (low battery consumption).

There are three fundamental approaches to coordinating the flash signal amongst a group of lamps.

  • Infra-Red Communication: Several manufactures choose to use a beam of infra-red light to communicate, much like your television remote control unit.  Much like your T.V. remote, you must properly aim the beam at the next lamp.  And much like your T.V. remote, if your cat or spouse gets in the way of the beam, you can’t change the channel.  Such is the case with the infra-red systems.  Anything that obscures or attenuates the signal will lead to asynchrony.  Fog, snow, rain, even the sun on the horizon can wreak havoc with the signal and interrupt the sequential pattern.  In addition, in areas of wind and high-speed trucking (truck wake), the mounting device (cone, barricade, barrel, panel, etc.) will tend to “creep” or walk.  This will eventually lead to misalignment of the infra-red beam and failure to synchronize. Range between lamps is quite limited with this technology because of the energy required to transmit a strong enough light beam.  One must take into consideration that when a lamp is damaged by impact, the two closest neighbors must now communicate across twice the distance. Finally, the lamps using infra-red communication must be positioned in a straight line, not positioned more than a few feet off of the center line.
  • Master-Slave radio communication: Radio waves represent a better choice for linking nodes, but now you have lamps chattering at each other much like a crowd in a bar.  They can all hear each other.  So, how do you make sense of all this gossip?  The Master-Slave approach basically requires the operator to designate a “Master” that will do all of the talking.  The “Slave” lamps listen and receive their flash commands from the master.  There are limitations to this approach.  First, the range allowed for the Master to talk to the last slave in the line is limited by the radio range.  So, the commercially available Master-Slave systems are limited to 10 lamps or so, providing a string of several hundred feet.  Second, should the Master be damage or deplete its battery, the whole gang must go home.  No synchrony.  Sorry, games over.  Finally, each lamp must be manually programmed by the operator as number 1, number 2, number 3, etc.  Takes time and knowledge.
  • Radio “Mesh” Network:  We left the best for last.  The progression from infra-red to Master-Slave to Mesh Network is a time chart of technology development over the past 20 years.  Mesh networks are now used in your home (Wi-Fi), cellular towers, and thanks to Pi Variables, Inc., in traffic safety.  In a Mesh network, all nodes (lamps) are equal; there is no Master or Slave.  Communication is via a 2.4GHz radio signal with range of 300 meters (1,000 feet).  So the distance between any two lamps can be up to 500 feet (have to provide for a missing lamp).  The advantages of the radio Mesh network is that there is no programming.  The lamps are smart enough to establish their own sequence number as you turn them on.  They can be remotely controlled from a distance of 300 meters (1,000 feet) from ANY lamp: Not just the first lamp.  So if you can talk to lamp 39, it will send the message to all the others.  Any lamp can control the entire network, even lamp 138.  The Mesh also allows for the lamps to be “sleeping” most of the time which leads to major energy savings.  Battery life on lamps using the Mesh network typically are 4 times that of the infra-red or Master-Slave system.  And unlike infra-red systems, obstruction and weather and sun angle and straight line deployment are not an issue.  Put them in a circle, around a corner, in a building around a corner, put work trucks between them, move them with wind and truck wake, whatever, the radio signal will find its way.


Besides the work zone scenarios, sequential warning lamps can be used in a number of different applications. To list a few: Parking lots for sports stadiums, concert/festivals, malls, school events, local city/town event, DUI checkpoints, short and long term police incident, crowd control, airport crosswalks, dangerous roads with curves, temporary cross walks, temporary runway “rabit light”, emergency evacuation, etc. 

Any situation where one needs to direct vehicles or pedestrians in and out of certain areas. 

Pi Variables, Inc. is a technology company always looking towards innovation.  Products in the pipeline that will use our patented Mesh technology include bicycle warning lamps, personnel lights, institutional building evacuation, and others more secret.


Pi-Lit® technology operates in the I.S.M. 2.4Ghz frequency band. This spectrum of radio frequency is dedicated to low power devices designed for  use in the Industrial, Scientific, and Medical industries (I.S.M.).

Indeed.  All of our products utilize a “System on a Chip” (SoC) with microprocessor (computer) and radio transmitter and receiver all on a single silicon wafer.  This component is FCC compliant and our circuit design has been tested by an independent laboratory confirming that spurious signals and radio-frequency output energy fall within strict FCC guidelines, and that the device is immune from external radio-frequency “noise”.

There is a mathematical limit of 256 lamps in a string. However, strings can be grouped together in an unlimited array effectively leading to a row of lamps without limit.

Yes.  Now we must be careful here.  There are 6 states (we think) that are a bit of a stickler on this issue. There is only one component in our product that is made overseas.  The bare circuit board is produced by manufacturers in China.  All other components are made here in the U.S. or by U.S. companies (for example, Texas Instruments).  The only other exception is our lithium batteries, which are manufactured in China.  All of our plastic is injection molded within 20 minutes drive of our facility.  Our electronic assembly of the circuit boards is performed in our building. Assembly and testing of the product is in our facility, as is design and support (when you call us).

The MUTCD is equivilant to the Bible for traffic control and traffic safety devices. All road projects, big or small, must follow the rules set forth in the MUTCD. Section 6F.83 permits the use of sequential flashing warning lamps on taper/delineator . Please view the below PDF to take you to section 6F.83 of the MUTCD.

Federal MUTCD 2012 6F.83 Sequential


Below are studies on the safety advantages that result from the use of sequential warning lamps. There are a number of studies preformed from department of transportation’s, independent organizations, and universities that have concluded that sequential warning lamps enhance safety. 

When looking through the research on sequential warning lamps provided below, please use the keyword search function in the document to scroll to their discussion on sequential warning lights



All Pi-Lit® Sequential warning lamps have a 1-year manufactures warranty. Any defect or issue with the lamp owing to manufacturing issues will be replaced by us.

Please call +1(949) 415-9411 or email info@pi-lit.com for more detail.

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