If you have limited space inside your phone and you need a ringer this may be your answer. Mini Electronic ringer or Warbler is very thin. Can be put inside phone using the RJ 11 jack or 2 spaded leads. Has 2 settings for the loud ringer. Also has a strobe light which you can disconnect if you don't need it.  This work great and are less than 1/2 the price vendors are asking for their warblers.