I'm probably late to the party on this. I wanted to do some paper workout home intervals and didn't want to spend the money on a timer. I came across this on youtube. There are other time/interval number options. Just thought I'd share in case someone is looking for a freebie!
6 Sets, 45 seconds work x 15 seconds rest timer - YouTube
6 Sets, 45 seconds work x 15 seconds rest timer - YouTube