What should we do if the power goes out and the Imam's voice is cut off while we are praying outside the mosque because there is no room inside?

If it becomes impossible for the congregants outside the mosque to follow the Imam due to a power outage, it is prescribed that one of the congregants near the door should loudly pronounce the takbir so that those outside can hear him and follow the Imam.

If they do not do so, the congregants have two choices: 1. Complete their prayers individually. 2. Appoint one of them to lead them in congregational prayer. This is preferable to avoid confusion.

Shaykh Ibn Baz, may Allah have mercy on him, held the view that the prayer of all is valid if they caught one rak'ah of Jumu'ah, even if they completed the prayer individually or appointed another imam.