You need to establish a digital reference.
If your oscillator will be your analog 0 reference verify it outputs 1.23 VRMS.

Your 192 or 96 I/O has potentiometer screws on the back.

Take the same oscillator, and feed it direct from the patch bay to you protools inputs, adjust the inputs to your digital reference level. (-18, -20). First set the reference in Protools/preferences, then turn on calibration mode, the bottom of the faders will indicate level.

Record the tone in Protools, play it out of Protools, set the electrical output of all channels to 1.23 volts RMS, that tone should now read 0dB on the console.

Now zero is zero is zero!!!!

Ah, an 80B, I made a lot of rock records on that baby in the 80s!!!!! Can you say Big Hair???

First thanks for your answer, I try to follow your tips but i'm nozt sure I made this right.
Ok, I explain you what I've done :-)
From My Trident Patchbay I used the oscillator (1khz), I send it into the channel 1 of my trident. Master Fader (0db), channel 1 Fader (0db), and the second red knob( below the gain Knob) from my channel 1 to 0db. I let the signal (from the oscillator) flow and from the output of my trident, i turned the oscillator volume knob to 1,23Vrms. In protools I gave -18 db as reference volume. I recorded my signal in protools into track one and i had (with the calibration mode from protools) -1.9db as input volume. So i turned all the protools input channel (input trim) to -1.9 db. After this, i used my recording signal for the outputs and I turned all these one (Protools trim) to the time I've got again my 1,23Vrms....
Is this right ?? or is there something I didn't understand.
Thanks to help on this way, because I haven't the feeling my recording to this time soundings right (about the output volume)..
Can you tell me also which output from the trident, should I use for my bouncing ?? I mean when I made my mix in Protools, i send groups in the trident again . What I mean is that I use channel 1-2 (from Trident) for guitars, channel 3-4 for drums, channel 5-6 for vocals, channel 7-8 for loops and synth, and channel 9 for bass...after this I have a sum from the trident that I send again in Protools through an another Patchbay..and for this I use the stereo bus output of the trident...is this also right ??
A lot of questions but I need a little bit support from pros...Thanks a lot again and hoping you can help me :-)
Friendly Sebastien

I recorded my signal in protools into track one and i had (with the calibration mode from protools) -1.9db as input volume.

Adjust the input trim screw until 0dB shows under the fader

Use a patch cable from the oscillator to the Protools input, NOT throught the board.
Dial the Oscillator to 1.23V adjust input trim in Protools to 0dB while in calibration mode.

Adjust the output of Protools to 1.23 V

Protools out put should now match the oscillator output when either is patched into the boards input.

No offense, it sounds like you do not have a full comprehension of signal flow. Signal flow is recording 101. I told you how to align Protools to match, signal flow should be completely understood before attempting to record anything.

Don't worry I don't understand you wrong, when you say I haven't full comprehension of the signal flow...and that's the reason why I write here :-)
I think the language makes the things harder because I can't explain the stuff in my own language.
I don't send the oscillator through the console and then in my input !! I send the oscillator in the channel 1 of my trident to measure my 1,23 Vrms output. Then I go directly from the oscillator to my protools input. Because how you want to know where is your 1,23V ?
You know my job is drummer. That means I get in touch with Neve, SSL, or whatever but I wasn't interested about signal flow, because engineers haven't time to explain you this when your in a major production :-) Everyone must make the first step and it cost nervs for the others ;-) So don't worry, you won't hurt me. Important is that i check these steps. I'm grateful you help me even if it's a bit confused.
Thanks