The Bisun S3 unit works in Fx3s, lead-acid powered Oldham lamps, Headlite headlamps using any Headlite battery, and other commercial or home-made systems with 3.6-4.5V power using regular Oldham or CEAG headsets.

The S3 uses the standard Bisun optical configuration, giving a bright spot beam which also has good down-spill for general caving, and a smooth flood beam for lighting up local surroundings more evenly. Independent electronics are used for each LED for maximum reliability.

The S3 reflector unit fits into Oldham and CEAG headsets, and is designed to run off nominal 3.6-4.5V power sources.

In the S3, each beam operates just as a bulb would, with a single fixed power level, and power being supplied to one or other beam via the switch, giving a choice of either spot beam or flood beam. Each beam runs at the same power level, drawing 350mA and producing about 140 lumens of light.

Compared to regular 3.6V/0.85A halogen bulbs, the S3 draws about 2/5 of the power and produces around 3.5x the light output.