Modes of operation
The HUD consists of three independent oxygen sensor monitoring circuits. Each circuit has two LEDs to signal the current pp02 range. Normal/safe diving mode is indicated by a solid green LED signal from each of the sensors. If a cell deviates from optimum pp02, the diver is signalled by LED flashes and/or colour change.
Display
The HUD can be connected into one to three oxygen sensors. If used with three independent sensors then it will function as a Primary HUD. With a single cell, it is an advisory HUD (no longer failsafe) and pp02 gauges must be monitored regularly.
LED signals
These are programmable by both pp02 threshold and associated signal. Required thresholds and signals are not user changeable but can be programmed according to individual requirements.
A sequence that might be used for an Inspiration-like setpoint controller is detailed below.
| pp02 range | Display signals |
|---|---|
| >1.6 | Red constantly on |
| >1.45 and <=1.6 | Alternate red/green flash (slow flash) |
| >1.15 and <=1.45 | Green on constantly (high setpoint) |
| >0.80 and <=1.15 | Alternate green on/off (slow flash) |
| >0.60 and <=0.8 | Green on constantly with off flicker (low setpoint) |
| >0.45 and <=0.6 | Alternate red/green fast flash |
| >=0.05 and <=0.45 | Alternate red on/off fast flash |
| <0.05 | Both off |
A KISS-style rebreather may have a single 'safe' pp02 range with alerts if pp02 goes above or below required levels.