Casano interval

On 14 March 1986, William Casano instructed the North Aisle Certification Workshop to retain three trials that its examiners had marked void. In each trial, an operator seated before an amplification unit had ceased speaking, lowered his head and failed to respond before the prescribed ninety seconds had elapsed. Casano’s instruction established what is now called the Casano interval.

I ask the certification committees, the hire companies and, above all, those who must sign their names beneath a result they did not design, to stop treating that interval as an embarrassment.

The disputed condition

The procedure is simple in description. An operator speaks into a microphone connected to a delayed return circuit. For ninety seconds, no colleague may correct him, touch the controls or disconnect the quarter-inch jack. The examiner records interruptions, repeated words, abandoned sentences, changes of volume and complete silence. The circuit is then isolated, whether the operator has continued throughout or not.

The question is not hypnosis, nor how to resist it, nor whether an examiner may fall asleep after a long shift. The question is whether loss of response belongs to the equipment trial or merely inconveniences it. The majority rule says inconvenience. I say evidence.

This distinction matters particularly with the Retort rig, whose delayed return can cause a speaker to restart the same clause several times. We already preserve stammering, reversal, laughter, whispered counting and the removal of headphones. Why, then, do we discard the one outcome that leaves the least room for interpretation?

The case for retention

Three objections are repeated.

First, we are told that silence proves nothing. Yet certification accepts absence elsewhere: absence of oscillation, absence of a return signal, absence of resistance at the selector, absence of movement in the level needle. Silence is not uniquely empty because a person produces it.

Second, we are told that fatigue contaminates the trial. Of course it may. So may room temperature, a loose chair, a late meal, an unfamiliar script, a stiff switch or the expectation that a colleague will rip the lead from its socket at the first irregularity. These conditions are recorded, not magically abolished. A tired operator does not make the apparatus disappear.

Third, we are told that the interval cannot distinguish a response to delayed speech from ordinary sleep. That objection is sound, but it supports classification, not deletion. Mark the result C for completed, I for interrupted, U for unresponsive. Add the shift time and the operator’s previous test count. Preserve what occurred. There is no dignity in throwing away an inconvenient line and calling the remaining page objective.

A limited proposal

I do not propose that every silence be attributed to the circuit. I do not propose extending the interval, repeating it immediately or preventing an examiner from ending a session when ordinary supervision requires it. The minority position is narrower: a trial conducted under the agreed conditions remains a trial when the operator becomes unresponsive.

The distinction has survived for forty years because committees prefer a clean total. Twelve attempts, two void, ten accepted, five passed: the arithmetic comforts everyone. Retain the two disputed attempts and the same session becomes twelve attempts, five passed, five failed, two unresolved. It is less elegant. After many meetings devoted to this matter, elegance is still the only practical advantage I have heard stated with conviction.

The Casano interval does not explain why an operator stops. It preserves the fact that he did. Until the profession can show that such facts belong nowhere, they belong in the result.

See also

• Bath fitting return — Retort rig
• Défense du décalage — Retort rig
• Delay-loop counter-drills — Retort rig
• Dons croisés — Retort rig
• Excursion allowance — Retort rig
• Grey reference case — Retort rig
• Lettre à Locations Belrive — Retort rig
• Lettre à M. Odilon Fasch — Retort rig