It happened on arrival back from school pick up during the week.
A moment which rammed home to us just how far things have progressed since our lives as children and that of our own kids.
"What's that mummy?," the eldest daughter said as my wife stopped at the front door step, bent over and picked up a small book which had been left there.
"It's a phone book, darling," my wife responded.
She was met with hysterical laughter by the 10-year-old and the seven-year-old trailing in her wake.
The mere mention of the words "phone" and "book" together as one, actual thing was something they could not get their head around. To them it sounded completely preposterous. Ridiculous in fact.
"What's it for?," the 10-year-old followed up with as she wiped the tears from her eyes;.
"Well ...," my wife explained. "It's a directory of people's phone numbers who live in the area so you can call them if you need to."
More hysterical laughter ensued. Fascinated, the 10-year-old then sat on the floor with this magical book trying to find the phone numbers of people in the area she knew, admittedly mostly teachers at her school.
"Oh, here's the phone number of Mr (name removed in fear of retribution) ... we can prank call him now," she squealed with delight.
It was at that point my wife had to explain that land phone lines were used only for proper personal calls, emergencies, automated calls from political candidates and overseas telemarketers.
Prank calling teachers was definitely not on, my wife reinforced ..... well, at least, while my wife or I were home.
You should have seen the amazement in her eyes when we explained to our daughter that at the same age, our household had not just one but quite a number of phone books and they were an essential part of any household.
Eventually the phone book novelty wore off and the eldest daughter wandered off to pick up her iPad.
Wonder what is going to be her "phone book" with her kids in another couple of decades ....
Julian O'Brien is editor of the Illawarra Mercury