Most storage devices that do not require vision and a brain to read data fall into this category. Electromagnetic data may be stored in either an analog data or digital data format on a variety of media.
Direct Tripwire Alarm - The wire placed across the path is directly connected with the cord, wire or string placed across the particular path. Laser Tripwire Alarm - An invisible laser, typically an infra-red, is used instead of a cord or string.
Typical wiring for current output transducer. You can think of the current loop itself as being analogous to a water system. You have a hose pipe (the wires) and a source tap (the power supply). You have a spray gun that regulates the flow (the transducer).You can have other equipment on the line, but it all has to be connected together in a ring Ioop. big benefit of the current loop is its simple wiring just the two wires. The supply voltage and measuring current are supplied over the same two wires. Zero offset of the base current (ie. 4mA) makes cable break detection simple: if the current suddenly drops to zero, you have a cable break.