What is a signal tower light? Classification, Applications, & Wiring guide

In modern industrial environments, communication and safety assurance are of utmost importance. One of the most effective ways to achieve both is by using Signal Tower Lights – multi-colored visual indicators that provide clear, real-time updates on machine, system, and safety status. In this article, we’ll explore in detail the definition, classification, operating principles, and how to select the most suitable Signal Tower Light for any industrial application.

Table of Contents

What is a Signal Tower Light?

Signal Tower Lights or Industrial Signal Lights are essential visual indicators in manufacturing and industrial environments. These devices consist of vertically stacked multi-colored LED modules designed to provide real-time status information of machines and systems, helping operators monitor equipment conditions from a distance.

Each color on the tower light typically represents a specific condition according to industrial standards:

Green: Normal operation, machine running.
Yellow (Amber): Warning, low material, or minor issue requiring attention.
Red: Serious fault, emergency stop, or hazardous condition requiring immediate action.
Blue/White: Additional notification, standby mode, or specific operating condition.

With advanced LED technology, modern tower lights are not only energy-efficient but also far more durable than traditional incandescent lights, improving both safety and productivity in factories.

Types of Signal Tower Lights

Signal tower lights are highly diverse and categorized based on various technical and functional criteria to suit specific working environments.

Classification by Number of Tiers/Colors

This is the most common classification, directly affecting the detail level of visual signaling:

1-tier Tower Light: Usually red or green, used to indicate a simple status (On/Off) or basic emergency alerts. Compact and easy to install.
2-tier Tower Light: Combines 2 colors (typically Red and Green) to indicate two basic conditions: operating and fault.
3-tier Tower Light: The most common type (Stack Light), using three standard colors (Red, Yellow, Green) to comprehensively indicate: Fault – Warning – Normal Operation.
Multi-tier Tower Light (4 tiers or more): Provides more detailed signaling for complex production processes, possibly including Blue and White tiers for additional states.

Classification by Alert Function

Beyond light indication, tower lights are also classified by additional alert features:

Light-only Tower Lights: Provide only visual indication.
Tower Lights with Built-in Buzzer: Integrated buzzer (usually above 85dB) to attract attention in noisy environments. Sound can be continuous, intermittent, or melodic.

Classification by Light Type

The type of light determines how the signal is conveyed and its urgency level:

Steady Light: Indicates stable operating status (e.g., machine running normally).
Flashing Light: Indicates attention or warning states (e.g., low material level).
Strobe/Flashing Light: Used for severe or emergency alerts requiring machine shutdown.

Classification by Shape

Tower lights can be designed to fit installation space and aesthetic requirements:

Cylindrical Shape: The most common design, ensuring optimal 360° visibility.
Square Shape: Used for applications requiring flat or angular design.

Classification by Operating Voltage

Voltage is a key factor for system compatibility:

Low Voltage (DC): 12VDC, 24VDC (most common, used in PLC control systems).
High Voltage (AC): 100VAC, 110VAC, 220VAC (used for direct connection to main power supply).

Classification by Connectivity Technology

Connectivity determines how well the light integrates into automation systems:

Wired Connection: Direct connection to PLC or relay output terminals.
Smart/Network Connection: Uses industrial protocols such as Ethernet/IP, Modbus TCP, or IO-Link. These allow remote tier-level monitoring, downtime tracking, and network-based control.

Operating Principle of Industrial Tower Lights

How Tower Lights Work

The operating principle is based on interaction between the control system and the signal device:

Connection and Control: The tower light is wired directly to production control devices such as PLCs, industrial PCs, or sensors.
Signal Transmission: When a machine status changes (e.g., cycle complete, technical error, or material waiting), the control system (PLC) automatically sends electrical signals to the corresponding control pin of the tower light.
Visual Indication: The corresponding color tier (Red, Yellow, Green) is activated to light up (steady or flashing), and the buzzer (if any) is triggered.
Immediate Response: This clear visual signal helps operators respond quickly, maintaining productivity and safety.

Difference Between Standard and Smart Tower Lights

Criteria	Standard Tower Light (Basic)	Smart Tower Light (Advanced)
Alert Type	Light or simple buzzer.	Integrated high-volume buzzer with multiple tones.
Connection	Direct wired tiers (Common + multiple signal lines).	Network connection (Ethernet/IP, Modbus TCP, IO-Link).
Application	On-site machine status indication.	Remote monitoring, IIoT data collection, SCADA/MES integration.
Features	Basic On/Off/Flashing modes.	Adjustable brightness, flash pattern, color, and self-diagnosis via software.
Durability (IP Rating)	Typically IP53.	High IP rating (IP65 or IP67) for harsh environments.

Applications of Signal Tower Lights

Signal tower lights are versatile tools indispensable in many industries:

Manufacturing and Production Lines: Indicate equipment status such as running (green), maintenance required (yellow), or major machine fault (red), minimizing downtime.
Safety Warning Signals: In hazardous areas, tower lights serve as essential safety indicators, providing immediate alerts about equipment or environmental conditions.
Equipment/Process Monitoring: In large facilities, tower lights allow operators and managers to instantly identify the status of multiple machines, prioritizing troubleshooting in real time.
Logistics and Traffic Control: Used in warehouses to manage forklift flow, indicate loading zone status (ready/busy), or at access control gates.

How to Choose the Right Tower Light for Your Application

To select the optimal tower light, consider the following factors:

Selection Criteria	Detailed Description
Operating Environment	IP Rating: Choose IP65 or IP67 for exposure to water, dust, or harsh conditions (food plants, outdoors). Choose IP53 for clean, dry environments. Material: PC/ABS housing for impact and heat resistance.
Brightness and Visibility	Diameter: Common sizes are 50mm, 60mm, 70mm, 80mm, 90mm. Larger diameters are easier to see from afar. Brightness: Ensure sufficient visibility under ambient lighting.
Number of Tiers and Colors	Select 1–5 tiers depending on the number of conditions to indicate. Use standard colors (Red, Yellow, Green).
Alert Function	Do you need an integrated buzzer? If yes, determine the required volume (usually ≥85dB) and sound type (continuous/intermittent).
Operating Voltage	Must match the control system’s power supply: 12VDC, 24VDC, or 100–240VAC.
Installation Options	Select suitable mounting type: base-mounted (on machine), pole-mounted, or wall-mounted.

How to Wire a Tower Light

Wiring a signal tower light is straightforward but must be done accurately to ensure safety and functionality. The general rule: all tiers share a common COM (Common) line, and each tier is controlled by a separate Signal line.

Before wiring: ALWAYS TURN OFF POWER to avoid danger.

1-Tier Tower Light Wiring

A single-tier tower light requires two wires:

Common Wire (COM/Neutral): Connect to the negative terminal (-VDC) or neutral line of the power source.
Signal Wire (Signal/Load): Connect to PLC or switch output. When this output is energized (+VDC or L), the light turns on.

2-Tier Tower Light Wiring

A 2-tier tower light requires three wires:

Common Wire (COM/Neutral): Shared for both tiers.
Signal Wire Tier 1 (e.g., Red): Connect to Output1 (activates Red light).
Signal Wire Tier 2 (e.g., Green): Connect to Output2 (activates Green light).

3-Tier Tower Light Wiring

A 3-tier tower light (most common) requires at least four wires:

Common Wire (COM/Neutral): Shared by all tiers and buzzer (if included).
Signal Wire for Red Tier (Output_red).
Signal Wire for Yellow Tier (Output_yellow).
Signal Wire for Green Tier (Output_green).
(Optional) Signal Wire for Buzzer (Output_buzzer).

Ensure all connections are secure and properly insulated.

Patlite Signal Tower Lights from Japan

Patlite Tower Lights

In the field of industrial signal tower lights, PATLITE (Japan) stands out as a global leader. PATLITE products are designed to meet the most demanding industrial standards, delivering exceptional performance in process management and monitoring. Their product lines, such as the LR series (LR5, LR6, LR7), are known for high durability, clear visibility, and integration of smart technologies.

Why Choose Patlite Tower Lights

Choosing Patlite tower lights offers strategic benefits for businesses:

Japanese Quality: Ensures high durability, stable operation, and LED lifespan up to 50,000 hours—minimizing maintenance costs.
Modern Technology: The LR-LAN (Network) series features Ethernet connectivity for remote monitoring and control, as well as OEE (Overall Equipment Effectiveness) data collection for IIoT systems.
Environmental Durability: Made from premium materials with high IP protection (typically IP65), resistant to dust, water, and impact.
Customization: Patlite offers a wide range of sizes, tiers, colors, and mounting options, easily integrating into existing systems.

Authorized Patlite Distributor in Vietnam

To ensure customers in Vietnam have access to high-quality PATLITE signal tower lights and alert solutions, Servo Dynamics Engineering is proud to be the official authorized distributor of PATLITE in this market.

As a trusted partner, Servo Dynamics Engineering is committed to providing genuine PATLITE products, including the advanced PATLITE LR5-LAN network tower light series, along with professional technical support and consultation services. This partnership ensures that businesses in Vietnam can easily integrate effective visual alert solutions, enhancing both safety and productivity in manufacturing and industrial environments.