The SKF electronic stethoscope is a hand-held instrument that is supplied in a sturdy carrying case complete with two probes, headset and batteries. A special multilingual bearing demonstration audio set of files describing typical bearing defects and related noise is available online. The noise or vibration from the machine is picked up by the stick probe and transmitted to an acoustic sensor where the vibrations are converted into an electrical signal, which is processed and amplified by the electronics of the instrument. The handset has two outputs for the amplified signal. One is for connecting the headset, the other to connect a recorder. The headset is an approved ear defender.