Say Hulloa! to commence the conversation : First Telephone book says

“Should you wish to speak to another subscriber you should commence the conversation by saying, ‘Hulloa!’, this one of the instruction found in the world’s first telephone book. The 20-page directory was issued in November of 1878, just two years after Alexander Graham Bell invented the Telephone. How to end the phone conversation, the book says, When you are done talking say, ‘That is all,’ and the person spoken to should say, ‘O.K.’”. Private collector Richard Green, had the book for many years.