You're both right

Main Entry: di·aer·e·sis
Pronunciation: dI-'er-&-s&s, British also
-'ir-
Function: noun
Inflected Form(s): plural di·aer·e·ses /-"sEz/
Etymology: Late Latin diaeresis, from Greek
diairesis, literally, division, from diairein to divide,
from dia- + hairein to take
Date: circa 1611
1 : a mark ¨ placed over a vowel to indicate that the
vowel is pronounced in a separate syllable (as in
naïve or Brontë) -- compare UMLAUT
2 : the break in a verse caused by the coincidence of
the end of a foot with the end of a word
- di·ae·ret·ic /"dI-&-'re-tik/ adjective

Main Entry: 1um·laut
Pronunciation: 'üm-"laut, 'um-
Function: noun
Etymology: German, from um- around, transformation
+ Laut sound
Date: 1852
1 a : the change of a vowel that is caused by partial
assimilation to a succeeding sound or that occurs as a
reflex of the former presence of a succeeding sound
which has been lost or altered (as to mark
pluralization in goose, geese or mouse, mice) b : a
vowel resulting from such partial assimilation
2 : a diacritical mark ¨ placed over a vowel to
indicate a more central or front articulation --
compare DIAERESIS

(From the Merriam-Webster online dictionary)

Geoff
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Got one of the first Mark 2 empegs...
_________________________
Geoff
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Mk1 Blue - was 4GB, now 16GB
Mk2 Red - was 12GB, now 60GB