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Pacemaker clock

The crystal of an implanted pacemaker. At a fixed pacing rate it beats at one constant interval that no device in the recording chain can touch, which makes it an independent reference.
Type oscillator
Nominal Fixed pacing interval (about 1,204, 1,000 or 860 ms in VitalDB's paced recordings)
Kept by Implanted pacemaker

Description

Only fixed-rate (asynchronous) pacing works as a clock. A demand pacemaker resets its interval at every intrinsic or fusion beat, so its phase cannot be carried across such a beat.

Route to UTC

The route the atlas trusts most (3 links; its weakest link is measured apart from the link to UTC that every clock shares):

Pacemaker clock
link measured Pacemaker against SNUADC
SNUADC sample clock
link measured SNUADC (frequent-correction mode) against the recorder PC: drift −0.954 ppm (n = 6321; census of 6,321 files (17 October): median −0.9535 ppm; 89.5% of recording hours within 0.05 ppm of −0.954; 747 files (12%) between −0.90 and −0.55 ppm)
Recorder PC clock
link assumed Recorder PC against UTC: drift 0.1–10 ppm (assumed); corrected every 8–24 h (assumed)
UTC
Where every route ends.

Independent checks. 3 other routes reach UTC; where they meet, the offsets must close around the loop:

Plan. Not needed for synchronisation: the pacemaker is a reference, used to test the SNUADC timeline. Its own absolute rate is unknown.

Link Clock Against Modes Rate Corrected every Status
Pacemaker against SNUADC Pacemaker clock SNUADC sample clock all — — measured

Parameters

Parameter Value Status From
Pacing interval agreement between stretches 0.05–0.1 ms measured Paced ECG as an independent clock

Studies

Study Date Status Summary
Paced ECG as an independent clock 2026-10-17 current Fixed-rate pacing gives a clock the recording chain cannot touch. Timing paced beats on three timelines shows that each SNUADC step-mode correction loses about 18 ms of signal, and that nothing else breaks the sample stream.