Table 1.

Details of the recording procedures in different subsamples

	N	EEG recording sites (10–20 system)	Polygraphic channels	Electrodes used	Effective sampling rate/sampling rate (Hz)	Precision	Hardware prefiltering (Hz)	Amplitude attenuation 10–15 Hz (mean [SD])	Recording apparatus	Recording software
Budapest–I	31	Fp1, Fp2, F3, F4, Fz, F7, F8, C3, C4, Cz, P3, P4, T3, T4, T5, T6, O1, O2	Left and right EOG, bipolar submental EMG, ECG, thoracic and abdominal respiration	Au coated Ag/AgCl fixed with EC2 Grass electrode cream	249/249	12 bit	0.5–70	0.9705 [0.0036]	Flat Style SLEEP La Mont Headbox, HBX32-SLP preamplifier (La Mont Medical)	DataLab (Medcare)
Budapest–II	16	Fp1, Fp2, F3, F4, Fz, F7, F8, C3, C4, Cz, P3, P4, Pz, T3, T4, T5, T6, O1, O2	Bipolar EOG, bipolar submental EMG, ECG	Au coated Ag/AgCl fixed with EC2 Grass electrode cream	4096/1024	12 bit	0.33–1500 (<450 Hz antialiasing digital filtering before undersampling)	0.9356 [0.0021]	Brain-Quick BQ 132S (Micromed)	System 98 (Micromed)
Munich–I	93	Fp1, Fp2, Fpz, AF1, AF2, F3, F4, Fz, F7, F8, C3, C4, Cz, P3, P4, Pz, T3, T4, T5, T6, O1, O2	Bipolar EOG, bipolar submental EMG, ECG	Ag/Ag-Cl, with EC2 Grass electrode cream for EEG and Nihon Kohden ELEFIX for EMG	250/250	8 bit	0.53–70	0.9693 [0.0016]	Comlab 32 DigitalSleep Lab	Brainlab, version 3.3
Munich–II	20	Fp1, Fp2, F3, F4, C3, C4, P3, P4, O1, O2	Bipolar EOG, bipolar submental EMG, ECG	Ag/Ag-Cl, with EC2 Grass electrode cream for EEG and Nihon Kohden ELEFIX for EMG	250/250	8 bit	0.53–70	0.9693 [0.0016]	Comlab 32 DigitalSleep Lab	Brainlab, version 3.3