EDIT Use
The pictogram is used to indicate the position of telephones in public places. It's also popular for substitution of the words »Telephone«, »Tel« or »T« that indicate a telephone number on businesscards etc.
EDIT Alternative for indicating a telephone number (here on a vehicle)
ADD NEWSIMILAR CHARACTERS
 < CHARACTER >  BLOCK PROPERTIES
U+2706 TELEPHONE LOCATION SIGN
DEUTSCH : ENGLISH