They are about the size of a medium sized mobile phone. They have metal electrical plates that when pressed to the skin act as recording electrodes. By pressing a recording button the machine is activated to record the patient’s heart rhythm for about 20 seconds. The patient can then ring a standard line telephone number and when connected press another button that sends the recording down the phone line where it recorded on an analyser and the ECG printed out. These kinds of recorders are particularly useful where a patients reports intermittent symptoms that last for a minute or more every few weeks as they can carry the machine around with them without any attached wires. They just have to make sure that they have the machine with them at all times and can find somewhere quickly where they can discretely place it on some bare skin on the chest.