The journalling reads:

As a teenager I wanted to maximize my sleeping time, but also not be late for work and school so this ‘alarm clock’ was devised.

Each night before I went to bed I’d set the clock to the time I needed to be up, and then I’d sleep like a baby (or more accurately a teenager) knowing that if I overslept Mum would wake me at the necessary time.

This arrangement worked extremely well – apart from making sure I was up when I needed to be, this system allayed Mum’s worries about me not being up when I should be.

And on a weekend it kind of acted like a peace-keeper: I could stay in bed as long as I wanted, but [there was tacit agreement that] normal house noises could commence after the time on my clock.