Đèn tín hiệu 200mm và 300mm khác nhau thế nào?

Updated 15 October 2026

200 mm and 300 mm describe the nominal diameter of the signal indication. They do not describe the overall housing width or the distance between mounting brackets. A 300 mm indication is 100 mm larger in diameter, but a catalogue size alone does not establish the correct choice for a road project.

Compare the complete signal, not just the diameter

Check the required circular, arrow, pedestrian or bicycle display, the number of sections and the approved optical performance. Lens design, aiming, background conditions and the installation position also matter. Do not assume that every 300 mm model has the same light output, or that every 200 mm model can replace an existing unit.

Start with the project requirements

The road authority’s specification should identify the permitted indication size and the evidence needed for approval. Record the approach direction, viewing conditions, mounting position and whether the signal serves vehicles, pedestrians or cyclists. Use this information to compare suitable models rather than assigning a diameter from the road name alone.

For a United States project, consult the current FHWA MUTCD together with the applicable authority’s requirements. A product described as 8 inch or 12 inch is not, by that description alone, approved for every installation. Other markets may use different specifications.

Replacing a 200 mm head with a 300 mm head

Treat the replacement as a configuration check, not a simple diameter change. Compare the complete dimensions, bracket centres, door-opening clearance, visor arrangement and cable entry. Confirm the supply voltage, terminal arrangement and controller interface from the proposed model’s drawing. The existing pole and brackets must be reviewed for the replacement assembly.

What to send with a quotation request

• The destination country, project specification and required indication diameter.
• The display symbols, colours and number of sections required for each signal head.
• The supply voltage and available controller or wiring information.
• A mounting drawing, or photographs and measurements of the existing assembly.
• The required housing material, quantity and any project-specific test documentation.

For a wider comparison, read the 200 mm, 300 mm and 400 mm size-selection guide. You can then send GAOQIAO the project requirements for a model and configuration review. Confirm the final drawing before treating two differently sized signal heads as interchangeable.