A Guide to Power Supply Symbols
The rating plate of an Extra Low Voltage Power Supply (ELVPSU) shows various symbols and abbreviations. These represent critical information about the supply's ratings, class, polarity, and other safety details.
DC Adaptor Polarity Symbols
The polarity symbol indicates if the centre (or tip) of the output plug is positive (+) or negative (-). Using the correct polarity is essential to avoid damaging your equipment.
Centre Positive: Indicates that the centre (tip) of the output plug is Positive (+) and the outer barrel is Negative (-).
Centre Negative: Indicates that the centre (tip) of the output plug is Negative (-) and the outer barrel is Positive (+).
Common Abbreviations
| Abbr. | Meaning | Abbr. | Meaning |
|---|---|---|---|
| V | Volts | Hz | Hertz |
| A | Amperes | PRI | Primary (Input) |
| mA | Milliamperes | SEC | Secondary (Output) |
| VAC | Volts AC | AC | Alternating Current |
| VDC | Volts DC | DC | Direct Current |
Safety & Construction Symbols
 Direct Current |
 Protective Earth |
 Class II Construction |
 Safety Isolating Transformer |
 Fuse Link |
 Short-circuit Proof Transformer |
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