Low Voltage Systems: The Unsung Heroes of Transit

In transportation infrastructure, low voltage (LV) systems often operate behind the scenes—but their impact is anything but minor. From passenger information displays to fire alarms and CCTV, these systems form the nervous system of modern transit environments. They don’t move trains or power escalators, but they ensure that everything else runs smoothly, safely, and intelligently.

What Falls Under Low Voltage Systems?

• Fire Detection and Alarm Systems
  These systems detect smoke, heat, or flame and initiate evacuation protocols. They’re powered by LV circuits and often backed by batteries or UPS for reliability.

• Public Address and Voice Evacuation
  Clear, intelligible announcements are critical in emergencies. LV amplifiers, speakers, and control panels ensure that messages reach every corner of a terminal or platform.

• CCTV and Surveillance
  Security cameras, network video recorders (NVRs), and monitoring stations all run on LV power. Proper cable routing and power budgeting are essential for uninterrupted coverage.

• Access Control and Ticketing
  Turnstiles, card readers, and biometric scanners rely on LV wiring and data networks to manage passenger flow and prevent unauthorized access.

• SCADA and BMS Integration
  Supervisory Control and Data Acquisition (SCADA) systems monitor and control electrical, mechanical, and environmental systems. These LV systems provide real-time data and remote control capabilities.

Design Considerations I Prioritize

1. Segregation and Shielding
   LV systems are sensitive to electromagnetic interference. I route them in separate conduits or trays, often with shielding, to preserve signal integrity.

2. Power Source Redundancy
   Critical LV systems are backed by UPS or emergency power to ensure they remain operational during outages.

3. Cable Management and Labeling
   With dozens of LV subsystems in a single station, clear labeling and structured cabling are essential for maintenance and troubleshooting.

4. Interoperability
   I ensure that LV systems can communicate with each other and with higher-level platforms like BMS or central command centers.

5. Compliance with Standards
   I follow PEC, NFPA 72, and NFPA 130 to ensure that LV systems meet safety, performance, and integration requirements.

A Field Insight

In one elevated station project, the fire alarm system was experiencing false triggers during peak hours. Investigation revealed that its cabling was routed too close to high-voltage feeders. Rerouting the LV cables with proper shielding eliminated the issue—a reminder that small design decisions can have big operational consequences.

Final Thoughts

Low voltage systems may not carry the heavy loads, but they carry the weight of safety, communication, and control. They’re the quiet enablers of a seamless transit experience. In every project, I treat them not as accessories, but as essential infrastructure—because when they work flawlessly, everything else does too.