What is the effect of the final telephone call upon the characters in 'An Inspector Calls'?

The effect of the final telephone call can be traced back to the very start of the play. Think about the way Priestley wants to portray the set. The first description of the set describes "a small table with a telephone on it". The telephone is in full view of the audience and you can it is always in the eyeliner of the audience. So when the phone finally rings at the end of the play, it is cathartic and cyclical to the beginning of the play. The final telephone call is a symbol of judgment and justice which you can also link to the religious aspects of the play - see day of judgment in Christianity. Other obvious links can be to how the playwright uses the physical prop as a vessel for suspense. The telephone call is a great way to show the examiner you know the effect of An Inspector Calls being a PLAY NOT A NOVEL. Good luck!