A number of modifications have recently been made to the electronic displays. These include extra switch on/off routines, a backlight feature with variable brightness, the "Check diluent" prompt has been moved to a position earlier in the start up sequence and there is an improved cell evaluation/validation during calibration. This improved cell validation rejects cells with outputs that are too low or too high, which also has the added benefit of preventing the diver calibrating whilst underwater.

The conventional lever switch is now a transit switch which completely isolates the electronics from its battery and should be used to preserve battery power whenever the time between dives exceeds two or three hours.

Switch On

Switching on now requires two actions: Firstly push the lever switch towards the screen. Then push the left slider towards the screen. This starts the display

The display sequence has been altered slightly:

• "Buddy Inspiration" (beep beep)
• "Elapsed On Time: xx hours xx minutes"
• "Dive Now, Confirm"
• "Check diluent, Confirm"
• "Calibrate Now Y or N / Must Calibrate Y or N"

From then on the sequence is the same as the manual with the exception of the "Check diluent" which has already been shown.

Backlight

Backlight activation is done by pushing any white slider towards the screen and releasing it. By pushing the left slider the backlight is activated for 5 seconds. By pushing either the centre slider or the right one (NOT BOTH) towards the screen the backlight is active for 15 seconds. Use of the backlight reduces the battery life.

The Brightness of the backlight can be adjusted to allow for varying climatic and ambient light conditions. Increasing the brightness reduces the contrast. Alteration of the brightness/contrast setting has no effect on the battery life.

Turning the brightness up to maximum in some conditions will make it impossible to read the display due to insufficient contrast between the figures and the background. Turning the brightness down to minimum in some conditions will result in black squares being displayed making it impossible to read the figures. A good starting point for UK conditions is to set the brightness between 20 and 40.

The Brightness adjustment is an option in the Menu Mode. You enter the Menu Mode on the Master in the same way as discussed in the manual - when the low setpoint is selected by pushing the left and right sliders (the outside two) simultaneously towards the screen. If both Master and Slave are on when you adjust the brightness the new value will not be stored for future dives. In order to make a permanent adjustment to the brightness have only one handset switched on, alter its brightness, leave on for 30 secs, switch off, switch on the other one and set the brightness on that one to the desired setting. Leave on for at least 30 seconds and switch it off. The new values for each handset will then be stored for future use.

If you do use the brightness adjustment underwater, please remember oxygen is not being added when you are in the Menu mode so the PPO2 is dropping all the time, dropping slowly but still dropping. Don't spend too long adjusting the brightness, get it done and get out of the Menu mode. The Menu mode has a time out, if you don't press a button for 15 seconds you are automatically bounced out to Dive mode, so please don't keep pressing one button every 14 seconds. Eventually, you will just go hypoxic.

Slave

Previously the sliders on the Slave didn't have any purpose. Now they operate the backlight for the Slave.

Cell Evaluation During Calibration

When they are new, the Oxygen cells (sensors) used in the Inspiration have an output of between 7.6 and 13 mVolts. With the new cell validation, the calibration will be dis-continued if the cell's output in oxygen is outside the expected cell output for cells outside the range 7 to 13.5 mVolts. If you see a cell out of range message on the display the cell should be changed prior to diving.

If you reset the handsets underwater, (why you would want to do this I don't know!) and see the option to Calibrate Y or N or Must Calibrate Y or N - you should select NO. If you accidentally say Yes, simply switch off and then switch on again, go through the selections until you reach again the option to calibrate and this time select NO. If you leave it to do the calibration the "Cell out of range" message will be shown, "no calibration". This prevents accidental calibration whilst underwater. At this point you should shut the handsets down and either go onto open circuit or go through the switch on routine again, being sure to select NO to the calibration question. Please be aware though that during all this the oxygen pressure is not being maintained by the oxygen controller, the PPO2 is dropping in the loop as you breathe - so don't spend too long adjusting, get the display back into dive mode where Master 0.7 is displayed on the top line.

The reason why you MUST NOT calibrate underwater: During calibration a quantity of pure oxygen is flushed into the loop. If you are at 50m you will be breathing 6 bar PPO2!. Convulsions will occur quite quickly. Do the calibration procedure only when you are on land, mouthpiece open, and NOT breathing from the loop.

The previous versions of electronics do not have the software to actually stop you doing a calibration underwater so on these models, it is a limitation of use that you must understand.

Switching Off

There are now two techniques for switching off a handset, both hardware. If the centre and right sliders are pushed towards the screen and held for a second, the handset will switch off.

CAUTION: When switched off like this though, there is still a power drain of 5mA, so the lever switch should be used if the unit is not going to be used for a few hours. Pushing the lever away from the screen isolates the display from the power supply.