プログレッシブ和英中辞典(第4版)の解説
ふつう【不通】
interruption [suspension] ((of telephone service))
東海道線は不通になった
Service on the Tokaido Line has been suspended [interrupted].／The Tokaido Line is not running.
大地震のため電信電話が不通になっている
Telegraph and telephone service has been interrupted [broken off] as a result of a strong earthquake.