Sigmapulse

Sigmapulse is the registered designation for the periodic survey emission by which Sigma-class regulators confirm the continued operability of pulse calibration systems on their assigned floors. The term denotes the emission itself, its recorded trace, and — by extension of long usage — the eighteen-minute interval following each emission during which the trace is considered live. It is not a machine, though it is routinely mistaken for one. Sigmagpulse, which is a machine, has petitioned twice for clarification of the distinction and has twice been refused, most recently under Third Concordance, Annex 9.

The survey interval is fixed at 18 minutes by the standing pulse calendar; the underlying calibration architecture is described under SigmaPulse and is not restated here.

Origin and first recording

The first Sigmapulse on record was logged on Floor 404 (the Floor of Unreturned Instruments) on 3 March, year 11 of the present recension, by the duty clerk Halverine Mott, whose hand is otherwise known only from a marginal note reading "again." Mott's trace is preserved in the annexe to Protocol Sigma-7 and is treated as the standard waveform against which all subsequent emissions are compared. It is the only document in the Tower that has never been amended, a fact the scriptoria mention with some resentment.

Early traces were recorded by ear, two clerks counting the peaks aloud in alternation so that neither could falsify the count. The practice was abandoned after the Alternation Dispute of Floor 622, in which both clerks were found to have been counting correctly and the trace to have been recorded twice.

The eighteen-minute interval

An emission is deemed live for eighteen minutes. A reading taken at minute nineteen is inadmissible, though it may be filed as an observation of the following emission, provided no emission occurred in between. Where an emission occurs during the live interval of its predecessor, the interval is said to have been overrun, and the overrun is reported to the nearest regulator in triplicate.

Jurist Sigma-1 has ruled on overrun four times and reached a different conclusion on each occasion. The rulings are collated in Line Sigma, which is consulted chiefly for the pleasure of watching the fourth ruling contradict the first by name.

"An interval overrun is not an error in the emission but an error in the interval. The interval should have been longer."

— Jurist Sigma-1, Fourth Ruling on Overrun, cited in Line Sigma, folio 41v

Relation to Sigma-class machinery

Pulse calibration systems of the high-energy Sigma class generate temporal eddies and inertial decoherence as a matter of routine operation, and the Sigmapulse is the instrument by which that operation is confirmed. The relationship is one of reporting rather than causation: the machinery pulses because it is running, and the Sigmapulse records that it has run. Chronal Streaking is the ordinary consequence of a live interval intersecting an eddy, and Inertial Echoes the ordinary consequence of its aftermath. Neither disqualifies a trace.

Where an eddy and a live interval coincide for the whole eighteen minutes, the emission is classified as a standing pulse and the floor is closed to traffic. Floor 119 has stood under a standing pulse since the winter of year 26 and is now entered on the tram schedules as a through-stop only. See Vertical Tram Line Sigma.

Disputed dating

Two recensions of the pulse calendar disagree as to whether the interval runs from the first peak or from the moment the regulator's lamp is lit. The Third Concordance fixes the first peak, Annex 9, clause 2. The Protocol 12-D recension fixes the lamp, clause 11, and adds that the first peak "is not a moment but a shape."

Neither document acknowledges the other, and the archive holds no ruling reconciling them. In practice clerks on most floors time from the lamp and file under the peak, which satisfies both offices and neither document. The practice is not authorised. It has been continuous since year 34.

Filing and custody

Traces are filed by floor, then by pulse, then by the clerk who counted. The third sort is the one in use and the one the Concordance forbids. Traces may be consulted by any holder of a reading warrant; reading warrants are issued at the Stairwell Sigma-44 desk.

Traces must not be carried through the Sigma Glassgpane corridor, as the glass retains the interval and releases it into a later floor's filing. This is not a prohibition on the glass, which is blameless, but on the carrying.

Peregrine-Sigma maintains the standing inventory of standing pulses, last revised year 47:

• Floor 119 — trades, textile, standing since year 26
• Floor 622 — stairhead, intermittent standing, unresolved since the Alternation Dispute
• Floor 404 — instruments, standing during the winter only

The inventory's fourth entry was struck out in ink and the strike is not dated. No office has claimed the striking, and the entry is legible beneath the ink to anyone who cares to hold it to the lamp, which the scriptoria formally discourage.

Sigmapulse was last catalogued on Floor 91, where the standing instruction on the ledger reads, in Mott's hand: "Count the peaks. Do not count the lamp."