Electronic apparatus for medical use, medical apparatus; patient monitoring, analysing and/or recording apparatus including digital apparatus; apparatus for investigating, monitoring, analysing, diagnosing and/or recording heart function and heart disorders including portable apparatus and holter monitors; apparatus for investigating, monitoring, analysing, diagnosing and/or recording electrophysiological variables including variables relating to the nervous system, neurology, cardiology and physiology; interface apparatus and sensors for monitoring patient variables including ECG (electrocardiogram), EEG electroencephalogram), EOG (electrooculogram), EMG (electromyogram), SaO2 (oxygen saturation), CO2(carbon dioxide), nasal air flow, patient movement including leg movement, thoracic and abdominal respiratory movement, heart rate, body temperature including rectal temperature, blood pressure, pH level, oesophageal pressure, snoring noises, CPAP (continuous positive air pressure) mask pressure, CPAP mask air flow, CPAP titration; radiology imaging aparatus including remote imaging and transmitting apparatus; telemedicine apparatus especially for medical purposes including equipment for teleradiology, teleconsultation and tele-echo-cardiology; computer hardware and software especially for monitoring, storage and replay of ECG data indicative of heart condition; communication interface apparatus especially for medical purposes including modems, apparatus for interfacing ISDN (Integrated Systems Digital Network), PSTN (Public Switched Telephone Network), SCSI (Small Computer System Interface), Ethernet, HIS (Hospital Information System), RIS (Radiology Information system), spread spectrum radio LAN (Local Area Network), FHSS (frequency hopping spread spectrum); apparatus for monitoring and/or displaying medical video and still images, including ECG and related data indicative of heart condition, including plotters and display monitors, video display monitors including CRT (Cathode Ray Tube), and flat panel displays including liquid crystal, TFT (Thin Film Transistor), and plasma displays; testing and/or calibrating apparatus for the above including apparatus for emulating physiological variables; parts and accessories thereof and therefor