In many cases, using such a defibrillator will alert emergency services. Very often, the defibrillator will guide the person helping through its use. In some countries such as the United Kingdom, regional public ambulance services provide lists for people to show where all the publicly accessible defibrillators are located in their region (East of England Ambulance Services Trust for example). In some open public locations, defibrillators are secured in special cases which need a code to open them (see the example on the right). When you call for an ambulance, you tell the operator the location code on the case, and they give you the code to unlock it to get the defibrillator out.