Using the Past Continuous with the Past Tense

When が先に来る場合は「、」（カンマ）が入る。
中央にWhen が来る場合は続けて書く。

* When I was taking a bath, the telephone rang.
= The telephone rang When I was taking a bath.

* While I was taking a bath, the telephone rang.
= The telephone rang while I was taking a bath.

* As I was taking a bath , the telephone rang.
= The telephone rang as I was taking a bath.

上記はすべて同じ意味。