Double speed is a non-standard setting where the ECG waves will appear twice as wide as normal. This is because the ECG is recorded at twice the normal ‘paper speed’. At this setting, the calibration signal at the start of the trace will be 10 small squares wide instead of the usual 5 squares. It has been said that this setting can help to visualise difficult P waves, but all it really does is stretch out the same trace without adding any new information. Using this setting can also create confusion because none of the normal methods for calculating rate, segments or intervals will apply. A better solution to uncover difficult P waves might be to record a full 12 lead ECG (because P waves might be more clearly seen in other leads), or consider recording a Lewis Lead.