Ten-four

When I was little my dad had a huge shop in the way back of the property.  He'd spend hours and hours back there working on Beauty, his 1941 Willys coupe.  We had intercoms in the house and the shop, and occasionally my mom would tell me to call Daddy and let him know dinner was ready.  So I would and I remember he would always respond "ten-four."  I had no idea why he liked those numbers so much or what made him pick them every single time.  I just thought he was funny.  So then I would say back, "ten-six!" or "ten-eight!" and giggle like crazy.