DOE-HDBK-1016/1-93ELECTRICAL DIAGRAMS AND SCHEMATICSElectrical Diagrams and SchematicsReadingElectricalDiagramsand SchematicsTo read electrical system diagrams and schematics properly, the condition or state of eachcomponent must first be understood. For electrical schematics that detail individual relays andcontacts, the components are always shown in the de-energized condition (also called the shelf-state).To associate the proper relay with the contact(s) that it operates, each relay is assigned a specificnumber and/or letter combination. The number/letter code for each relay is carried by allassociated contacts. Figure 14 (A) shows a simple schematic containing a coil (M1) and itscontact. If space permits, the relationship may be emphasized by drawing a dashed line(symbolizing a mechanical connection) between the relay and its contact(s) or a dashed boxaround them as shown in Figure 14 (B). Figure 14 (C) illustrates a switch and a second set ofcontacts that are operated by the switch.Figure 14 Examples of Relays and Relay ContactsPR-03Rev. 0Page 14
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