i stucked in the part of the big factory..help!!

[almogpr]

hello....i passed the first chapter of the game...(exploding the northen area with TNT)..after i blew it up i entered to some factory with 3 rooms (one of them is power room) in the factory there was a guardian dog with a gate and i dont know how to open it..i'm stuck on that level i dont know how to continue..i picked up some stuff (like broom and communication device) and thats it..i dont know what to do next..can some one help me plz???