HVI Live Line Indicator 1500V DC
The High Voltage DC Live Line Indicator (LLI) is a battery-operated electronic unit specifically designed for testing DC systems. It is particularly relevant for Mass Transit Railway (Metro) and Tram-based models. While usually applied to overhead catenaries, it can also be used on "third rail" installations. Providing proof that a system is de-energized—and can therefore be safely earthed—is critical for the safety of maintenance staff and system security.
Three versions are available to cover the most common system voltages: 750V, 1500V, and 3000V DC.
Operation and Alarms
The DC LLI provides both visual (high-intensity flashing red LEDs) and audible (70dB) alarms if a conductor under test is live. Each version features a threshold setting of approximately 33% of the system voltage; any voltage above this threshold deems the line energised.
The unit is operated via a simple testing sequence:

Arming: Pressing the test button activates the alarms to verify they are working.
Ready State: Upon releasing the button, the red LEDs are replaced by green ones, and the audible alarm stops. 
Testing Window: The green "safe to test" condition remains active for approximately 5 minutes. If the unit is applied to a line and the threshold is exceeded during this time, the warning alarms will reactivate.
Battery Check: Pressing the test button also performs an automatic battery health check.

Versatility
A universal "star wheel" adaptor is available to connect the unit to various operating poles. Additionally, alternative clamps are available to suit different earthing systems, such as buried rails.
Live Line Indicator Kit
Each complete kit comprises:

DC Live Line Indicator with earth lead & clamp
Bowthorpe Rod Adaptor (incorporated into the indicator case moulding)
Universal Star-wheel Adaptor
Hook, Y, and straight electrodes
Polymer Cleaning Kit
Comprehensive Instruction Manual
Durable Carry Satchel