ABSTRACT
This chapter deals with electrotechnical control systems that perform safety functions; such systems are commonly known as safety-related control systems or electrical/electronic/programmable electronic safety-related systems. It provides an overview of the main devices used and the principles that underpin the achievement of adequate levels of safety. The interfacing arrangement between the electrosensitive protective equipment and the machinery control system is a particularly important facet of the safety system's design. It is the overall control system incorporating both the Active Optoelectronic Protective Devices and the machine's safety-related control system that determines the level of safety that can be achieved. For many years, processing units in electrotechnical control systems were implemented using electromechanical devices such as relays, switches, and push buttons. A minority of accidents in the machinery sector are the result of control systems failures.
