 left blank Introduction 23/3 Introduction Global consultation with test houses and approved authorities is recommended, especially in cases of doubt or ambiguity. This chapter covers two topics which are of paramount importance in the consideration of any system, telecommunications or other- wise. 23.3 Basic elements of telecom safety These topics are Safety and Electromagnetic Compatibility (EMC), also often known as Radio Frequency Interference (RFI), Some years ago IEC produced IEC Guide 105. This distinguishes and they relate to personal and network safety, and as such they are between three objectives: controlled by government regulations. In its least harmful form RFI is a nuisance, but in others it can 1. Safety of the user from electrical hazards in equipment (see lead to dangerous situations, for example when it causes inter- Figure 23.1); ference in systems such as aircraft navigation and life support 2. Safety of network service personnel, and other network users, systems within hospitals. from hazards in the equipment (see Figure 23.2); 23.2 Safety This section deals with the design of safe telecom equipment, in particular in compliance with the available standards for safety. Which standards are to be used will probably be in the product specification and adherence to every aspect is necessary. The fol- lowing guidance gives the background and principles to facilitate understanding these complex documents, and deciding what to do when the standards do not fit the case. Emphasis is on the technical content of the standards, rather than the means of demonstrating compliance with them, or the legal framework in which they are enforced in some countries. Standards in Europe are the main consideration, because the situation (in 1992) is moving towards an unprecedented harmonized enforce- ment regime to facilitate movement of goods throughout the region. The situation is, however, far from stable and it can be foreseen that Figure 23.2 Safety of network personnel and other users there will be some changes