Machine safeguarding, presence sensing devices control machine operations and protect personnel by detecting the presence of objects that could interfere with or be harmed by machinery. Activating a machine safeguarding, presence sensing device sounds a warning, ends a process, initiates a different machine action, or stops the machine altogether. Several types of devices are commonly available. Area guarding systems are used to monitor large areas such as shop floors. By contrast, perimeter guarding devices are designed to monitor the edges of machines. Door and gate guarding devices prevent employees from entering restricted areas, typically during machine operation. Process protection devices are used to protect personnel during equipment service and maintenance. Machine protection devices are used to monitor and guard operators during normal machine operation.