The Egyptian hieroglyphic script contained 24 uniliterals (symbols that stood for single consonants, much like English letters) which today we associate with the 26 glyphs listed below. (Note that the glyph associated with w/u also has a hieratic abbreviation.)
The traditional transliteration system shown on the left of the chart below is over a century old and is the one most commonly seen in texts. It includes several symbols such as 3 for sounds that were of unknown value at the time. Much progress has been made since, though there is still debate as to the details. For instance, it is now thought the 3 may have been an alveolar lateral approximant ("l") in Old Egyptian that was lost by Middle Egyptian. The consonants transcribed as voiced(d, g, dj) may actually have been ejective or, less likely, pharyngealized like the Arabic emphatic consonants. A good description can be found in Allen.[1] For other systems of transliteration, see transliteration of ancient Egyptian